Operationally, it makes sense to have them both on the same radio system, as they are geographically close and respond with mutual and automatic aid to each others' jurisdictions. Same goes for forwarding all fire/medical calls to WCCCA, at least for streamlining the process.
Logistically, it starts to get interesting, with a lot of issues to decide. Will Newberg retain all of their existing dispatchers, or will some be offered a lateral transfer to WCCCA? And WCCCA's possible future move to digital with the upcoming bond measure means that new equipment such as radios will need to be purchased/leased. This isn't cheap, especially for smaller departments. And both Newberg and Dundee have existing VHF pagers and UHF comms., and will likely need to retain part or all of that for mutual aid to the rest of Yamhill County. Which brings up the question of whether the paging system will be able to be accessed by WCCCA.
And... if the residents of Newberg decide at the end of the contract not to renew it, all or most of these infrastructure and personnel changes will need to be reversed.