Not likely, at least in anything bigger than a small town. It's a lot easier for the EOC to program a few radios with each primary public works channel and dispatch them on their individual channel than it is to rely on communicating with everyone on the same VTAC. Especially when you're placing a lot of people on that channel who aren't used to using a radio, now your open mic or feedback issues affect everyone, and the higher levels of traffic cause public works users to turn their radios down which causes them to miss calls.
I'm much more likely to keep public works on their own channels, or if they rely on a repeater which goes down, to switch them either to another public works channel, an OEM or a spare "tac" channel, or possibly an itinerant or even GMRS frequency (any port in a storm) that I know isn't in use rather than a nationwide interop that is likely in high demand. I understand that a lot of municipalities can't necessarily rely on having someone in the EOC who understands what frequencies may be available and is able to reprogram radios as needed, but having that ability is much more valuable to me than committing one of a limited number of channels to public works. It probably also helps that we have pretty good relationships as far as comms goes, in terms of everyone knowing what everyone else has available and public safety and amateur groups that are willing to share resources.