GECAS will only provide GE family engines.
Nope. GECAS will finance whatever the deal requirements are.
Many of their leases are for non-GE powered aircraft which they finance for the airline. It's only for aircraft they order directly (for instance with the Q8 or 6N
Boeing codes) which are always GE
or CFM powered.
Lead me not into temptation, I can find my own way there...