I know what you are getting at, I just couldn't resist....
The vultures or the naughty bits?
The common reason for not using BPL is that you need to "hop" over the transformers, and the equipment for this is expensive and interferes with HAM radios and other wireless traffic.
Smart grid is the name given to technologies that provide advanced capabilities to these "last mile" customers
I think you are thinking of Advanced Metering (AMI). Smart Grid is the integration of Generation, Transmission, Distribution, Retail, and Consumer technologies.
Now if you had the data elsewhere, and you wiped the the device, you would be safe because you are not destroying the evidence. This is best for you as a defendant as they need to make the case to a hopefully independent judge that the data is related to what you were arrested for. At this point, the prosecutor would have to know how the data is related, and can't just ask for "all data that was on the phone that shows you are guilty of X", and they can't ask for anything not related to what you are charged with. (Wikipedia's US v. Hubbell article has a good example of what they can ask for.)
Your state law may vary, and arguing constitutional law to a cop probably won't help.
The spoliation inference is a negative evidentiary inference that a finder of fact can draw from a party's destruction of a document or thing that is relevant to an ongoing or reasonably foreseeable civil or criminal proceeding
I am no bible scholar, so this is just my observation
Your contract may state that they are not allowed to mine or even store your filtered data, but how would you ever know? Good luck executing an eDiscovery search on largest collector of data in the world. I'm sure the attorney's would love it though.
I think it is called Postini.