For us, they waited long enough for things to start running on there own again. It took about 11 hours for some of the imports to start. They did however confirm our suspicion about limited resources within the response to our ticket:
"Because TEST is a testing instance, it doesn't have as many resources so it runs a bit slower which is why the import process took a little bit to finish. This also can be affected by traffic of other institutions utilizing TEST at the same time."
Although this response suggests that the resources for Test are different than for Prod and Beta, my guess is that when it comes to the sis_imports they are all tied together. Why they couldn't cancel a problem import or add resources on the fly is a mystery to me. But fortunately for us, both Prod and Test are now functioning again.