The plot thickens... aerial photos taken recently suggest that Sub-Terra is currently a hive of activity, and a local engineer has promoted that they are working on the ride on Twitter:
Interestingly, the photos show that a new queue line is being built on top of the old boards... which would certainly suggest that the building is being reused, in my eyes.
It should also be noted that this engineer referred to the ride as "Nemesis Sub-Terra", for what it's worth...