No, carriers are not required to disclose their transmitter locations
and there are no comprehensive 3rd party websites that have this
information.
The only information that is available is if the structure (tower) is
over 200' tall, close to an airport, or if the antennas on an already
existing structure (building) extend 20' over its current hight. And
even with this information there could be numerous carriers at the same
location, but they are not required to disclose that they exist there.
The structure information is registered with the
FCC.
The only carriers required to "site license" are NEXTEL (now Sprint)
and SoLinc who are ESMR's and conform to
FCC Part 90 rules.