Yes and I have seen some of them, and I do believe some guys do pass on numbers. I've actually had someone pass on the address - ok so the guy wants to know where he's going but it was scary when he said he really didn't know the address, then phoned from right outside my door saying "is it number x?". Not very discrete

I do however still carry out my own usual screening, if they sound like they aren't going to get on with me, or behave like a bit of a knob on the phone then I'm going to be declining fairly quickly.
Someone once rang claiming someone had given him my work number to ask advice on a hobby in my personal life that I supposedly know something about, nothing to do with sex work. He refused to tell me the person's name for fear of getting him into trouble, err well in that case why pass a prossie's number around for 'advice' why not stick a few words in google or ask a business locally dealing in that area

I do believe some guys think that saying they've been passed your number will provide some sort of explanation that might make me feel reassured, it's a form of introduction, or make themselves feel as if they've not been searching for prossies.
Whatever reason it really doesn't seem to make any prossie feel comfortable.