How about this:
If we have all day to track 100 positions and looking for the cheapest solution.
We install 100 remote receivers (micro + RF) and sample the IF (20 to 30 MHz) for 10 to 20 seconds (100 MBytes)? We can transmit this with a slow serial link to a central station.
We can then process this 10G data in DGPS mode, using the Philips's software solution.
Will this work?