GMP seem to be really mixed. On the hand, officially all specials are aligned to the INPT teams, and should parade on and work with them. Unofficially, lots of us work response, take on jobs etc. I'm not interview trained personally, but the training is available (albeit its the regular weekday course).
Personally I mix double crewing with response officers to working single crewed. Single crewed in theory I'm INPT, so usually start off doing INPT taskings, but response are that short, most comms ops just send us to jobs the same as the regs. I'll often be the only patrol available for grade 1 jobs (which is where GMP's driving policy is really frustrating).