The only way to do it automatically would be to have the spotter aircraft in the same group as the soldiers. If you are happy using someone else's script, then something like GroupLink II shares information between groups for you.
To do it yourself, I'd go through the list of
nearTargets for the plane every few seconds and for each one,
reveal it to the group of soldiers. If you want the aircraft to call out positions and directions, then there are a few
functions at OFPEC that could help: SPON_directionName, GetRCoord and/or GridCoord. I think you'd need to make sure the server view distance was enough to allow a plane at 1000+ metres up in the air to actually see anything on the ground.