Yes, they can test for Omicron and many other variants, most of which never catch on. They’ve doing that for a long time.
Here’s Colorado’s current variant testing results:
https://covid19.colorado.gov/data
Scroll down, you’ll see all the variants Colorado is following. Omicron is (as of yesterday) .07% of Colorado cases. They even show which counties have cases and how many.
The myth that there’s no way to test for variants is wrong,
Full disclosure, I’m not vaxxed and don’t plan to be.
Wide spread testing vs in select labs?