Don't you need some sort of administrative access to the switch? Its not like a vendor can plug in a laptop in the conference room and sniff out our emails during his powerpoint? -- * seek help if having trouble coping --Standard disclaimers apply.--
And the OP's question might need explaining more, as there is a yes/no type answer to the question. Yes a VM will allow sniffed traffic. Will it allow all traffic to be sniffed? Depends on the network. Hence my comment initially on what is the network we are referring to from the OP, it is too broad a comment I'd think to give an exacting reply. Call me pedantic.