Hi @Pauciloquent ,
I didn't have the chance to test the script itself, but if your are collecting the proper data in your property bags (see belolw hpw yyou can test thiss - the artcle i pasted), then the steps that you need to do to make the script work, are descriibed here (an article I wrote about how to integrate a PowerShell script with SCOM) and run it on your SCOM management server:
Monitoring Active Directory User Account Expiration using SCOM and PowerShell (Step by Step Guide)
You will see in the article how to test you script and make sure it returns the right proerty bags and also how to integrate in SCOM. It has also nice screennshots and lots of details. Please post back if you need further help.
(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)