Hmm, I´ve tested it in Hamburg, Stuttgart and Frankfurt. But with no luck. When I spawn on the gate,I can call the jetway. (which is of course nonsense for this litte plane, it just looks funny)
Spawning on the ramps makes no difference either.
All other options via the ATC are not available.
The Toolbar pushback is a nice tool, but even with this I´m unable to call any ground service.