Amtrak works with Zones for its T&E crafts. When you are hired say in Miami you are hired into Zone 6. This establishes your seniority both within Zone 6 and nationwide for whichever craft you are hired in. You may bid on any jobs posted nationwide with the understanding that you will only be paid to qualify for a different Zone if the Carrier is in need of manpower. If the Carrier has not posted a "cover sheet" (for their weekly bids) Pay To Qualify for a specific Zone/Crew Base, then you will qualify for said job on your own dime.
Back to Zone 6 in Miami if you will. Say you are hired as a conductor and are qualified between Miami and Orlando (as a conductor). You have rights as a conductor to bid into the Jacksonville crew base as a conductor if a position is showing vacant on the currently weekly bid sheet. But since you have not been qualified between say Jacksonville and Orlando, you would qualify on your own time until the trainmaster sees fit that you posses the knowledge of the territory between JAX and MCO. If the Carrier has a cover sheet pay to qualify for that JAX job or a conductor vacancy and you have enough seniority to bid onto the job, then you will be paid to qualify.
Zone 6 as an engineer out of Miami. You are promoted from a conductor or off the street as a re-entry engineer from say a freight railroad. The carrier will pay for you to be qualified between Miami and Tampa (engineers only run to Tampa out of Miami while the conductors travel to Orlando and back). If after you qualify as an engineer and you wish to transfer to the JAX crew base as an engineer you can do one of two things. Just as above with the conductor, you can either bid to JAX and qualify between JAX and TPA or transfer on a union rule 6I. A 6I allows you to bid within the Zone you are currently qualified in and be paid to qualify in another crew base by the carrier. If you bid into JAX without a 6I then you will not be paid and you will have to run and learn the territory on your own a minimum number of times before you are qualified. This can certainly bite into your pocketbook real fast if you are not a quick learner.
Say you want to transfer from Miami (Zone 6) to Denver (Zone 11). You can do so as long as you have the seniority to do so but you will not be paid. Even if a vacancy as an engineer is showing a 6I pay to qualify, you are not "found" in the zone 11 and will learn the territory on your own time again. Now, if the carrier on their weekly bid sheet has a "pay to qualify" on the cover sheet for Denver, you may bid on it and if awarded the job, the carrier will pay you to qualify at straight time until you are qualified over the territory. The carrier will not however pay for any moving expenses, travel to denver, etc. You are on your own in getting to Denver from Miami.
That is the quick and dirty version of what is needed to bid to/from different zones. It's not as in depth as I'd like it to be but it gets the point across.