it is really inplemented. to communicate with ground crew for rearming and refueling (door closed, and electric power to radios), you need to set the intercom control to the "ground crew" setting, and the R-828 radio must be on channel 9 for them to communicate - otherwise, you will never get a response. same thing with ATC: you have to set the radios correctly in order to communicate - otherwise, you will hear your own sim voice, but never get a reply because they never hear your transmission. very cool...
*edit: um, the R-828 does NOT need to be on channel 9, i found out.