Project 25 is the Public Safety (Police, Fire, EMS) system. The county also uses Project 25 for Public Works (streets, solid waste, etc) along with the regional jail. The Project 16 is used by the city for Public Works (streets, solid waste, etc) and for Valley Metro and School operations and as a backup for the city Public Safety in case of problems with the Project 25 system.
So if you want the county it is all on P25. If you want Police, Fire, EMS they are primarily on P25.
Basically the Project 16 is the old system for both but the city elected to keep it in place and operational as a backup and for non-public safety users.
Roanoke City Public Safety do not use conventional channels as their primary communications except for the Sheriff's Office. They are on UHF while the rest of Public Safety primarily uses the P25 system. The City Sheriff's Office uses UHF for the jail and court duties but they use the P25 system for the deputies on the road (civil process servers) so they can interoperate with the police. They primarily use UHF for better in building coverage at the jail and courthouse.
The county also does not use conventional channels for Public Safety as a primary system. They do have some conventional channels they use as a backup in the event the P25 system is down while the city first uses the P16 system as a backup with some conventional channels as a secondary backup.
The county does use conventional for school buses while the city has the schools on the P16 system.
Yes, Vinton is on the P25 system while they maintain some conventional as 'chat' channels.