Changing UDIDs on apple devices is very simple, you just need to know what you are doing...
So is this person you? It's not so simple you have to jailbreak your device and go through a lot of effort. Android simulators come with this already as an option, or simply reinstalling does the trick.
In any case nearly every person gets lazy and does not change ip and udid every time. OTM then just cross correlates them (a small amount of work) and then goes ahead and bans them all.
I've seen this happen in other mmos so it definately can be done.
Had this same person try it on me in teranis yesterday. I spam shouted that they are a scammer, reported them, and then pmd them some 'friendly' words.
Btw put your collision files back in. It's annoying to have people mod the game when the rest of us play legit.