Answer: Yes contract has been formed.
Explanation: According to the Uniform Electronic Transaction Act (UETA), electronic transactions are just as binding as transactions made on hardcopy documents. Moreover signatures made electronically reinforces the validity of these elctronic documents.
In the scenario the actual signature was signed on a hard copy by the seller, but it was then faxed back to the listing agent. This faxed copy, showing the faxed signature, is an electronic document that confirms the existence of the contract in accordance with the UETA. This faxed signature is as enforceable as an ink signature.