When UPS and the Teamsters gear up to negotiate a new National Master Agreement they will usually start no later than one year before the expiration date of the current agreement. This is done to alleviate customer concern of a potential work stoppage. It wouldn't surprise me if they started even earlier this time as 2013 promises to be a contentious negotiation process as I think UPS intends to have us begin paying for a portion of our healthcare . You should also keep in mind that in addition to a NMA there are local supplements which address needs and concerns unique to that area. For example, here in Upstate NY we have procedures in place to deal with snow emergencies which obviously would not apply to employees in Florida. The bid process varies from area to area.
I think you guys should plan on at least a year between being given the right to unionize and the ratification of a contract--it would more likely be closer to 18-24 months.
Also, don't think that you are irreplaceable. FedEx has technology in place, through your handheld scanners, to hire replacement drivers. They can also easily divert volume to Ground.