A urethane (i.e. two-pack) clear can be applied over any sound, compatible surface. If the substrate is fully cured then it will need thorough scuffing or sanding to provide a mechanical bond but, if this preparation is done properly then the clear will last just as long as it would over freshly applied basecoat.
Most repairs are done by blending the base over and beyond the repair area and then extending clear to the end of the panel, obviously over the existing clear. A urethane clear will bond to a surface that has been well scuffed with grey Scotchbrite or P1200-P1500. Basecoat over a cured substrate needs a coarser preparation of P600-P800.
To be honest, I think that clear over a cured substrate is actually better. Far too many painters rush the clearcoat application in the push to get cars "out the door" and this is one of the primary causes of clearcoat separation as the solvents in the base haven't yet fully flashed off and actually push the clear off as they try to escape.
Although it wouldn't be that cheap, reclearing a new, or near new, car would have a number of advantages. Certainly cheaper than a respray later it would provide (assuming quality clear and correct application thickness) a much better layer of protection which would take surface scratching repair without becoming too thin. It would also allow the opportunity to wetsand the surface to completely flat, getting rid of that horrible dry finish that is typical on Mazdas and Thai built utes and ending up with something that is orange peel free with a really deep gloss. If I had the time I'd do it to my own car while the paint is still in good condition. Big job though - needs all exterior trims, seals and glass removed first so there are no exposed edges.
If work is so terrific, why do they have to pay us to do it?