For the profiles, you can simply edit the templates dealing with profiles (I want to say showuser.tmpl is the primary one) to just not display e-mail addresses at all. Just find the appropriate part of the template for that, and comment out that code.
Signatures would be a little more complex, as you'd have to parse their signature for URLs and addresses and remove or replace them. Much simpler would be to simply turn off signatures (if there's not an option to disable them entirely, set them to a length of 1 or something).