From my basic reseach (going from memory here)
Need to have 30 years in, and at least age 60. If your younger, you need to work more than 30 years, but when you hit 60, your good to go.
Tier 2 with a wife works out to be 150% of your salary, or thereabouts. I am still deciphering the fine print, but thats what it looks like. I believe an average of some of your highest years comes into play. Its in one of the RRB .pdf files.
If you jump RR's, as long as they have been defined as conducting interstate commerce (99.9% are), RR retirement applies. If you go to work for an industrial railroad (steel mill owner, etc) these typically are not considered a common carrier, and you would covered under the companies retirement plan.
Only thing you lose is your senority from the former RR to the new RR unless you somehow cut a deal.
If you leave RR employment, your done. All your money stayes with the RRB. After a certain time, there may be a way to have some/all of your contrubitions rolled over back to SS. Again, information is in some of the RRB .pdf files.
Vested means that after x amount of years, upon your retirment from service, you are entitled to receive the monies. If you leave before your actual service committments are completed, but are "vested" you will received a greatly reduced check (sometime as much as 90% depending on lenght of service/age/etc) than what you would have had if you stayed. I don't remember off hand, but I think once you leave the RR field, your done (unless you go out on disability retirement) and you get no cash.
But as mentioned, a call to the people who do this all day is the best source of information.
http://www.rrb.gov/forms/PandS/g177series/g177.asp
http://www.rrb.gov/forms/opa/ib2/ib2_overview.asp
http://www.rrb.gov/forms/opa/ib2/ib2_re ... Connection
If my comments offend you, then I guess I did my job.