Here's a basic script, how I'd do it (for what it's worth)
#RESTART
~5
_teammates = units player
_teamcount = count _teammates
~2
_i = -1
#LOOP
_i = _i + 1
? ((_teammates select _i) hasWeapon "LSR_prc117new"): hint "Laser Radio in Group"; RadioEquipped=true; goto "RESTART"
? (_i == _teamcount): goto "NORADIO"
goto "LOOP"
#NORADIO
RadioEquipped=false
hint "Radio no longer in group"
goto "RESTART"
exit
Obviously, it changes the value of RadioEquipped depending on the presence of the radio; I don't know if that is useful or if you'd have to merge your Radio Call scripts with this.
A possible flaw might be if the radio operator has been killed, and the player hasn't noticed, that is said "Oh no. Seven is down!". Until his icon has been removed from the command bar, is he still considered part of the players group?
My original idea was, rather than check for the radio's presence, check for its use through an eventHandler. All units in the players group would run the following script:
_man = _this select 0
_man addEventHandler ["Fired", {if ((_this select 1) == "LSR_prc117new") then {[_man] exec "RadioCall.sqs"}}]
exit
Unfortunately, Laser's radio doesn't seem to fire - it doesn't trigger the script and it doesn't deplete the batteries. Also, I don't know if team-mates could be ordered to fire it.