While most TCAS I and TCAS II antennas are manufactured by Sensor Systems for other manufacturers, they all possess different part numbers and models numbers. Some even will indicate a Sensor Systems part number. However, that number indicates proprietary part number and status that Sensor Systems will have with the manufacturers such as Honeywell and L3. You cannot purchase the TCAS antenna with the Sensor Systems part number direct from Sensor Systems.
Regarding interchangeability, there are very similar characteristics between the various TCAS antennas. However, it is not so much the functionality characteristics that determine the interchangeability as it is the certification. That is, since an L3 antenna part number will not be listed in a Honeywell TCAS STC installation manual, you cannot substitute one for the other.