I wouldn't think it'd be a problem. Unless, somehow by "1 ISP" you mean you have the same IP address, but I doubt that's possible. My friends and I have played over ICO while a few of us were in the same house before (laptops). You should be fine.
Edit: I think this is the first time I've beaten Annatar to answering a question. I feel proud... and yet, so very ashamed.