[quote=@Mr Allen J]
You don't really under - if Mika copies two similar powers, they'll combine together. So I assume that her current telepathic abilities will receive a boost.
[/quote]

Per my earlier statement I don't think Mika would want Lucy's powers. It would be like listening to headphones on low volume then suddenly you've got a boom box on max volume blasting in your ear.

[quote=@Shard]
I am more interested in what happens if two telepaths read each others minds at the same time. 
[/quote]

I think there are two probable outcomes. Either two telepaths trying to read each others minds would hear absolutely nothing like two standing waves cancelling each other out or they would get everything with no coherent order or relevancy to what they were looking for, like a tidal wave.