I can see two problems with disabling communications city-wide with such an approach. First - any cell phone, not in the line-of-sight with the jammer is not going to be disabled. And second - FCC and network ops would locate the jammer and disable it.
To make this attack successful, one need to put the transmitter sufficiently high, and make it mobile. Flying it on a conventional airplane wouldn't work, because air force, FAA and police would be on such high profile case in no time. Flying it on the UAV RC helicopter could be a solution, but given the weight of the transmitter, antenna and fuel, that makes the resulting setup rather heavy and expensive to make and operate - well above 10k. A large tethered balloon also wouldn't work, because it would be spotted in no time.
All and all, this attack just wouldn't work city-wide.
To make this attack successful, one need to put the transmitter sufficiently high, and make it mobile. Flying it on a conventional airplane wouldn't work, because air force, FAA and police would be on such high profile case in no time. Flying it on the UAV RC helicopter could be a solution, but given the weight of the transmitter, antenna and fuel, that makes the resulting setup rather heavy and expensive to make and operate - well above 10k. A large tethered balloon also wouldn't work, because it would be spotted in no time.
All and all, this attack just wouldn't work city-wide.