The hight would be an advantage, and you'd get free power - the best of both worlds. You could put a transmitter (complete with inductive pickups) in place, then fly the drone back for reuse. It would also be quite hard to take down, even if they knew it was there.
I wouldn't worry too much about cloaking. The police are not going to risk their necks climbing up a power line to take out a ~$30 transmitter, unless it's to get prints or the society in question is very Orwellian (in which case, you can't make the drones anyway, because Big Brother is watching). I'd just go for transmitter which are too cheap to bother fighting against.
It's a low power device. They'd press charges if they caught you (to discourage other people doing the same thing), but it's not worth sending out counter-surveillance operatives to trace the device, then calling out a couple of linesmen to take it down simply to save power. A 60 watt device (my laptop running at full power) costs ~$70 a year. A Raspberry Pi, even with a reasonable Wifi transmitter, costs far less. And I bet the cost of power at a distribution line is less than what a consumer pays for power in their home.
As someone who lives in a society enabled by cheap, centrally generated electric power, I'd actually kind of hope the power company would seven-figures go after somebody who steals it from their distribution network, even if it's just somebody who wants to watch Game of Thrones without HBO.
The aren't going to fire a varmint rifle into the air in a populated area. They might want retrive these to get fingerprints or DNA samples, so they could chase down whoever put it there (and the MPAA / power companies might lobby for them to make this a priority), but I doubt they'll do anything dangerous simply to take down the devices.
I wouldn't worry too much about cloaking. The police are not going to risk their necks climbing up a power line to take out a ~$30 transmitter, unless it's to get prints or the society in question is very Orwellian (in which case, you can't make the drones anyway, because Big Brother is watching). I'd just go for transmitter which are too cheap to bother fighting against.