You don't need a paper ticket to swap airlines; an e-ticket will do. Other carriers often match the gov't contract carrier fares but there may be other fees involved in swapping your ticket with regard to taxes. For example, one airline may charge the fuel surcharge to government tickets but another airline may not. Also, if your original ticket was nonstop and you swap out your ticket and the new ticket is not nonstop then you have extra PFCs.