Hi James,
Depends on your definition of a lab tag. In PI server terms I considered a lab tag to be a tag that belongs to Pointsource L.
How the data is populated for a tag belonging to Pointsource L is no different to a tag that belongs to another Pointsource. Typically I see PI-UFL used for loading csv files of data from lab systems.
Cheers.
Principal Consultant
Real-Time Data Management @ Wipro Technologies