In fact there already is a similar arrangement in force at the moment whereby geostationary satellites use their last drop of fuel to raise themselves up to higher orbits to free their slots just before their missions are terminated. The development of a shuttle service for moving satellites around could as it matured help reduce the launch economic and environmental costs. This could be achieved by launching geostationary bound satellites into lower orbits initially, thus reducing fuel requirements and then allowing the shuttle spacecraft using the solar powered ion engines to transfer the satellites to their target orbits higher up. The biggest problem would be devising ways to protect the satellites while crossing the Van Allen radiation belts during the transfer. Turning now to the military class of satellites, not an awful lot is known, but the numbers are considerably less than the commerical sector.
Military satellites cover a broad range in terms of function and orbit.
The best known are the spy satellites, but these themselves are varied too. In this category there are spy satellites working in the infra-red and optical range and generally in low orbit. Then there are the low orbit radar satellites use for terrain altrimetry mapping and ocean survelliance. Again these tend to be low orbit. The second group of the spy satellites cover those listening and eves-dropping on radio traffic and communications and these would tend to be in higher orbit, presumably geostationary or thereabouts.