I don't understand why it couldn't be possible that this tank will not go through the cycle. If the LR and LS were transferred to the tank without too much time out of water, there is no reason to believe that the bacteria died off. I'd just consider it the same as a massive water change.
The existing LR had been around long enough to have plenty of bacteria living in it, even if some had died off during the move. AND if that happened, then the living bacteria should have been adequate to contain the spike.
What is really, really important is to get a good quality test kit, with measurable results. If you test ANY nitrates, then the tank has cycled, or entered the final stage of the cycle.
“Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.”
-Jim