I went through the process of getting a prepaid sim card when I was there. It pretty much took a whole day out of my schedule. Photocopies of passport, visa and completion of a length form(in triplicate) and I had to provide multiple passport photographs. Returned the form to the vendor who then had to get it approved by an agent from the provider before he could issue me the SIM card.
This was last year and I think I read somewhere the rules for foreigners have been tightened further.