1) Project 25 a.k.a "P25" long predated Katrina. P25 is a (supposedly) open-standard "design-by-committee" digital mobile radio standard still incomplete after 25 years of effort.
2) An incredible amount of mis-information about P25 floats around among non-technical managers, politicians and government officials that keep repeating the post-911/post-Katrina mantra of "interoperability". The most egregious lack-of-understanding is that somehow merely owning and operating a "P25-compatible" network will "automagically" make you "interoperable" with other agencies. They fail to understand that P25 only defines a transmission protocol. P25-format transmission can be used on any of 4 or 5 different frequency bands from 30 MHz to over 900 MHz. Most radios and antenna systems only operate on one of these bands. The 30,000+ public-safety entities (federal, state, county and local) in the U.S. are scattered across all of of these bands. Or that IF several agencies that, by luck, do operate in the same frequency band show up at a disaster, that they still won't be able to talk to each other until considerable software tweaking and radio re-programming is done to make the digital addressing of various groups' radios match, in a manner somewhat similar to making LAN subnets mesh. (Unless of course, mutual-aid common shared channels are agreed upon in advance. This is common in adjacent jurisdictions such neighboring counties, or city police-vs-county sheriff in a given county, or counties-vs-state-patrol in a given state. However it all falls apart in scenarios like Katrina where diverse public safety groups from several states away show up to help.)
3) In fact, a brand-new P25 statewide public safety network had been turned on in Louisiana only months before Katrina, but failed massively due to the ravenous power demands of the complex P25 base-station and network-controller infrastructure. The modest power demands of classic "dumb" analog two-way radio base stations (10s of watts/channel on standby/hundreds of watts on transmit) can be backed up by battery banks at remote sites for days or even weeks at a time, possibly supplemented by solar or wind power.. The massive power demands of P25 systems with dozens (or even hundreds) of racks of power-hogging computer controllers, routers, servers and always-on-and-transmitting control-channel transmitters at each site means a continuous standby drain of 10's OF KILOWATTS. Typical battery backups can only provide a few minutes run time with this kind of drain, until fossil-fueled generators can (hopefully) start up. Typically the on-site fuel supply (usually diesel or propane) is good for 72 hours or so. However, the extensive flooding and general chaos made it impossible for fuel tankers to get to the sites for the first week or so. One-by-one the sites just ran out of fuel and shut down.
4) The sorry history of P25 in (more or less brief)
Over two decades ago, digital systems first started being proposed as a replacement for 50+ years of analog FM radio in commercial & public-safety mobile communications. Numerous proprietary digital protocols were pitched by manufacturers and basically went nowhere because each protocol was available from only a single manufacturer, eager to lock-in customers like police and fire departments to a single supplier for the life of the system.
Project 25 was undertaken by APCO (Associated Public Safety Communications Officials -- essentially the police and fire radio lobby) to define an open digital comms standard beholden to no one manufacturer.. It was grossly complex, as the result of being the typical design-by-committee responding to an endless stream of "It would be really nice if it could do
For nearly a decade, many vendors played lip service to offering P25 hardware at trade shows and conferences (at least on paper!) but didn't really push it -- they really didn't want an open system, where like analog FM, you could buy compatible hardware from multiple vendors. To make things worse, APCO turned over the publication, maintenance and ratification of updates of the standard to the TIA (Telecommunications Industry Association). TIA is the trade association and lobby of the land mobile radio manufacturers, who (surprise!) had little incentive to revise and update the standard in a timely manner. Each TIA member had the vested interest in promoting their proprietary protocol.
It wasn't until the FCC "narrow-banding" mandate for land-mobile channel splitting from 25 to 12.5 KHz channels (the drop-dead date for the switch is supposed to be Jan 1, 2013) that P25 took off at all. Users were faced with either turning down deviation on analog FM radios to 2.5 KHz (to cut the occupied bandwidth in half) yielding radically poorer audio recovery on existing equipment. Or replacing ALL their hardware with newer radios, repeaters, trunking controllers, etc so why not go digital as well. Using agencies responded by typically adopting a wait-and-see attitude and stopped buying anything since the narrowband drop-dead date seemed so far in the future. Under pressure largely from federal land-mobile users such as the FBI, Border Patrol and the U.S. Forest Service, vendors were finally forced into offering REAL P25 hardware. This was largely achieved by the feds offering substantial funding for new radio networks, but ONLY if they were "P25-compliant".
The problem is that, as of the mid 2000's, "P25-compliant" was still a mushy ill-defined mess with many mfrs offering "P25-compatible" radios not fully compatible with other mfrs models. The DOJ charged NTIA to do an evaluation of then-existing P25 radio offerings to identify ones that were "interoperable". The idea was to give those that were a sort of "Good Housekeeping Seal of Approval" that would make them eligible for federal funding for purchase by federal, state and local public safety agencies. The whole process fell apart due to political infighting in Washington.
5) After nearly 20 years, P25 is STILL an incomplete work-in-progress quasi-standard grudgingly accepted by the major radio vendors who would STILL rather lock you into a proprietary digital protocal for life. By the way, nearly ALL radio manufacturers, outside of Motorola and "the company formerly known as GE in Lynchburg, VA" that is now part of Harris, (i.e. the second-tier land-mobile vendors like Icom, Kenwood, BK Radio, Johnson, etc) offer P25 radios by incorporating modules made by Motorola.