Presently there is no "flowthrough" agreement from Tyrolean to Austrian, although there are talks to implement such a thing.
Working at Tyrolean doesn't prevent you from applying at Austrian but it won't help either. Austrian will require a separate selection with tougher medical criteria and tougher criteria on maximum age (
AFAIK).
You'll lose money paid for your Tyrolean typerating if you leave before Tyrolean has paid the typerating, which usually takes 5 years these days.