I can't speak for all digital radios, but P25 and MOTOTRBO radios feature a conventional analog operation mode.
It should be pointed out that no one has definitively confirmed that the Town of Chester is going with MOTOTRBO. I am simply pointing out that they have two pending applications with the FCC to add emission type 7K60FXE, which is for MOTOTRBO voice. It's also worth noting that the Village of Chester already has the 7K60FXE emission on 155.040, which they added back in March.
In any case, it has nothing to do with any 800 MHz system. The Town and Village both have operating capability on NYCOMCO's 800 MHz EDACS system already. The VHF frequencies are separate from that, and are licensed to the Town and Village, not the county or NYCOMCO.
I'm not exactly sure what "800 MHz buildout" you're referring to. I'm by no means an expert on all things OC, however I haven't heard anything about "PD going to 800" or "FD/EMS going to UHF". FD is moving fireground operations to UHF, but the VHF paging and Low Band operations frequencies remain. EMS is still operating on VHF, as are the PD's MRD and 911 Polling frequencies. I think you need to check your facts on that one.