This is a topic where some mechanics disagree. I say replace not resurface. My reasons are as follows;
1: Volvo advises against machining rotors.
2: If a Brake rotor is out of round. you would have to machine way too much material to bring back true.
3: If the rotor has ''hot spots'' (bluing), the hot spots go all the way through the rotor. Machining the rotor will make the rotor all shiny, but the hot spot is still there, and this is where cracks come from. (metal brittlement)
4: Volvos are heavy cars and removing material from the rotors deminishes braking capacity. IE: rotors will become hotter. The bigger the frying pan, the longer it takes to heat up.
5: California has way too many ''injury attornies''. (ambulance chasers that are standing by to sue anybody who touched the VIQ.)
6: Once material is removed from the rotor, the chance of it going below minimum specification is dramatically increased.
7: I'm not the one who let my brake pads go too long.
8: The chance of brake pads (repco) squealing when installed w/new rotors is 0.

I don't change the rotors every time I do brakes. As a matter of fact, my customer w/645,000 miles is on his 1st replacement set. Different drivers have different brake service needs. I don't change rotors because they have shallow grooves in them. That doesn't matter. What matters is, that the rotors are true, and above minimum specification.
Do yourself a favor. Replace the rotors, install PBR full metallic pads w/stainless steel and teflon shims, and have your mechanic install the new ATE rotors that have the cooling grooves. They look like someone used a spirograph on them. Front pads part # D143M --
George Swift / volvo car care