Yes. Typically you would somehow populate the actuator interfaces when initializing your RobotHW specialization, and then use the TransmissionInterfaceLoader class to automatically populate your joint interfaces from the URDF + the actuator interfaces.
I thought there were no code examples available, but it turns out that I did write some doc back in the day. It's just not very visible. Please see the TransmissionInterfaceLoader class code API.
The above only deals with populating interfaces. You would then need to actually propagate the transmissions in the read/write methods of your RobotHW. Please refer to the main transmission_interface Doxygen page for examples.