DFC,
Go look in the AIP and read what it says about (not) entering CAS if you haven't yet received a specific joining clearance.
As for an RA, it should be a vertical maneuver of a few hundred feet, which is fine and if it may slightly infringe CAS before returning to previous level that's no big issue. It's not a climb to flight level nosebleed and continuance en-route. Don't consider it a 'safety reason' for entering or continuing either else what are you doing operating on your PC sim from an airfield outside CAS in the first place? You want max safety and protection, don't fly in Indian Country.
Sorry.