It's unlikely that this sort of thing happens, let's get that out of the way - especially in something like dubstep. But with, say, a rock tune, it's not unheard of to snip the chorus and raise its level by a little bit to 'lift' it if it helps the song. You might need to snip a bit out, ease it back not to push the compressor so hard and then nudge it back up after to keep level without so much comp in that section, or the opposite for more, or eq that bit up but only that bit, blah blah. This kind of thing is generally quite unusual though!
Sorry this is a bit vague!
Basically it's almost impossible to say what would be done without having track in front of you. No presets in mastering, everything is taken on an individual basis 
It all depends innit
