Whirly,
That used to be the case with analogue links but with the advent of CODFM digital links the more multipath (i.e. terain problerms) the better, you just put in more ground stations.
Also with a heli 'mid point' each car had to be selected as to which was required at the time and only a limited number of cars could be linked at one time, but with ground pickup you could in theory have every car available all the time (with sufficient ground channels)
So its the end of sitting at 3000' on the edge of vortex ring (I have done that a lot as an ITV Links engineer and PPLH)
Cheers