I have done some testing and at the moment AI wingmen within your own flight outright refuse to launch BVR radar-guided missiles at A-A targets. Other allied groups and enemy AI will still launch these weapons, but when commanded, AI wingmen will simply push until they are within range of an IR guided missile and, assuming they've survived that long, will fire an AIM-9 or R-73 instead. This absolutely applies to all versions of the AIM-54 Phoenix and all versions of the AIM-120 AMRAAM across all airframes. It also appears to apply to the AIM-7 Sparrow and the R-77. The only oddball exception seems to be that AI MiG-29 wingmen will still engage using R-27Rs & R-27ERs. The Su-27 and J-11A both seem reluctant to use any version of the R-27 and follow the same script of flying toward the enemy until within range of their short-range heat-seeking missiles.
In these tests it also seems as though the wingmen never actually turn their radars on at all, even if directly instructed to do so.
I believe this behavior is the result of the most recent Open Beta update as these same missions were played a few weeks ago with AI wingmen launching these weapons at will.
The simplest way of testing this for yourselves is to fly the F/A-18C BVR 8v8 Instant Action mission. You will notice that the second flight will launch their AMRAAMs and Sparrows, but your own wingmen will not.