Does anyone know if there is a way to manage modular vehicle locks with Oxide? I have tried existing hooks CanLock(), CanUnlock() and CanUseLockedEntity() however none seem to work with the new vehicles.

There is not. The existing Oxide hooks would only have worked if the game devs used the existing entity classes for the locking functionality, but it's basically all new code. We could add Oxide hooks for the car locks, but there are some issues such as the client not even sending mount requests when showing the locked UI.

I eventually just implemented code locks for cars which so far I like a lot better. My plugin for it executes it pretty flawlessly.
https://umod.org/plugins/modular-car-code-locks.

Damn, that's what I figured. The plan was to create a keyring plugin to hold your keys instead of them using inventory space. Although your code lock plugin basically does the same thing and is much more elegant.