Sorry for the late responses, folks..
@razo+r, I did set the freq for the FAC beforehand and made sure a preset was loaded into the radio before mission start. As for the ATC, I was on the ground at Kutaisi, made sure I was on the correct preset (again, set before mission start) and I tried multiple times to contact ATC for taxi to no success. But If I restarted the mission and tried again, it would work. I couldn't quite get it to do this consistently enough to really go into detail. I tried every possible version of PTT / Radio / communications button available in the controls menu so I'm not sure.
@Flappie, Much appreciated. I've been back and forth with the L39 and the A10 so you are probably 100% correct and it may not have the JTAC Item. But I would be really cool if it were added. Again, thanks to both of you for your help!