Trimble radio question...Will this work

I use a 450 MHz GPS base and rover. The base is an R8 without a radio, uses an external Trimmark III. Contractor now has all 900 MHz setups. Question is, can I stick a 900 radio in the R8 base I have and use it as a rover when I'm on a site where their base is already set up, and still use it as a base with my 450 Trimmark III and rover?