I don’t think it is a bad idea to enter VHF channels as they are used if Safe-T system goes down. Some Fire Dept. use VHF channels for fire ground where there is a chance a P25 trunked radio can’t hit a site from inside a building. Some Agencies that still have VHF High Band or UHF radios besides a trunked P25 radio might use the VHF/UHF radio for car to car or on scene traffic control.
Most trunked systems in rural areas are contracted to provide 95% coverage with a mobile radio (typically 25-45 Watts in 700/800 band). In Metro areas the coverage is sometimes contracted to provide 95% coverage for portable radios (2-4 Watts).