The same thing is happening in the aviation world-- most aircrews are required to carry around several thick, heavy binders around with them all the time, and always keep them up to date by pulling and replacing a bunch of pages every month or two. I'd guess your average pubs bag weighs 30-40 pounds, depending on the aircraft and crew position. iPads are becoming common as a replacement.
This is the sort of thing a tablet is perfect for-- content consumption. In an otterbox it's plenty durable, the battery lasts a long time, it has a big, pretty, readable display, and in the long run it will actually save money over paper. You no longer have to issue a full set of pubs to everyone (initial issue can cost several hundred dollars), updates are basically free, and hilariously there's also a measurable fuel savings due to the hundred-odd pounds of paper you're no longer hauling all over the world. It's not a perfect system, and there's work to do on the updating process and overall formatting (I lose all my annotations every time there's an update, and the PDF files don't come with nearly enough bookmarks), but most of those problems come from the fact that pubs are currently written to be printed. Once they're formatted with a tablet in mind, I expect things to get better.
Obviously the article's implementation of the technology is quite different, but I wouldn't be surprised if there are similar advantages to be had for a police force. Remember that the iPads are likely cheaper than the laptops they are replacing, or if there aren't laptops to replace (the article doesn't say) they are saving man-hours somewhere. Labor is expensive.