Yes, that's what you do (I'd use a 1 to 2 or 1 to 3 outlet adapter to keep down the cabling spaghetti).
The probe for the RHPs goes in one of the cages, either secured to the wall nearest the RHP, or dangling under it. I was told by Reptile Basics to have the probe around 6" below the RHP. The probe for the UTHs goes on one of the cages per PitOnTheProwl's sketch.
You do need to check that the temps in both cages are good, even with identical RHPs and UTHs.
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