Goes both ways. I have T2's on mine and wanted them machined. They had no run-out but did have a slight taper due to some heavy abuse. Took it in to be machined at a reputable specialist. Got it back, taper was gone, but now the rotor had run-out that was more than double the factory max tolerance.
Took it back and said 'Oi!'
They run em up again, but still the run-out was not within factory spec. I know by this point I've wasted man hours pulling thebortors off and putting em back on, and they could not try to mahine again as the rotor would become too thin. They assured me it would be fine, and i got them to sign a receipt and put a 10,000km warranty on it. Just in case it ended up with pulsation or uneven contact and they'd buy me some new T2's.
Anyway, morale to the story, with single piece rotor and hubs, it's probably best to just get them replaced. Or have them machined on the car. they are difficult to machine off the car due to the inbuilt bearing cups and require a very accurate jig to get right.