There is a lot of information on the web concerning cutting holes in porcelain tile and glass. We just used that same information to cut a hole in the Domsjo sink deck. The Ameriglas website seemed to have the most useful informaiton concerning what is involved in drilling a hole in this type of material.
Disclaimer: I'm no expert at this. If I can do it, anybody else can do it too.
Domsjo Sink: Drilling Additional Holes
Domsjo double bowl with additional hole drilled.