I was able to get the Information that I was looking for by using this script from Andreas Baumgarten on the SCSM Technet Forums:
import-module smlets # Get the extended class $GetClass = Get-SCSMclass -Name ClassExtension_$ # Get the object of an extended class ID equal RA68 $GetObjects = Get-SCSMobject -Class $GetClass| Where-Object{$_.ID -eq "RA68"}
#Output Title of the extended Review Activity ID equal RA68 $GetObjects.Title
The Format List alias was helpful in showing me all the available properties in my extended workitem.
$GetObjects|fl