They don't distinguish between different Cats when giving a track limit. Although they talk of a limit, in practice I've never seen any official actually checking a rider's gearing. I tend to look on the limit as a recommendation rather than a strict rule.
Tracks are usually designed with a specific gear range / speed in mind, and this is where the Calshot limit came from. In practice, these things tend to be self-enforcing anyhow - if a rider turned up to race with a 90 inch gear at Calshot, they'd be spotted pretty quickly while in the bunch, and if they looked any good, would be opening themselves up to being attacked repeatedly until they're tired. It takes much more energy responding to repeated short attacks if you're overgeared.
This is kind of assuming bunch races / sprints - being a steady solo effort pursuiting is a different kettle of fish...