The problem is that a thief would just turn the phone off immediately, when it is stolen, long before you ever report it as a stolen phone or even realize it was stolen.
Not being able to remove the battery could be an advantage in this case :)
1) in situations where phones are not meant to be switched on (e.g. some flights)
2) from a privacy perspective not being able to ensure your phone is actually off is not great.
Nice try, but that's a long way from a (long running, secret, and still hidden) vast government/corporate conspiracy to remotely power on any smartphone to spy on the owner.
It was quite discussed at that time. for example: http://www.tomsguide.com/us/nsa-remotely-turn-on-phones,news...