Does that cover your question?

That's a complicated question.

When you hold a job at a crew base as either a Conductor or Engineer you are either on the spare (extra) board or a regular job, when your on the spare board you are subject to call in whatever territory that your crewbase covers and when your regular you have a
assigned run.

here's an example, lets say your currently assigned to the formally run by Amtrak M.B.T.A. trains working out of North Station now the MBR Spare Board, your normal Crew base reporting locations are:
Boston's North Station, Fitchburg, Lowell, Reading, Haverhill, Ipswich, Newburyport, Rockport and Beverly Ma., all of these reporting locations are covered by the Northside Trainman's, Conductors and some of them by the Engineer Boards, Conductors and Engineers (Both Organizations) have separate
agreements by contract with the Carrier(Amtrak). they call you in compliance with the contract (check out usrail.net to see an agreement) which is no less that a 2 hour call for both of these crafts to make any one of these reporting locations at any hour of the day in any type of weather no matter what... you have to be there or you loose your guarantee ( 40 hrs pay). Most of the time you know what job you're going to
cover if you follow the vacation schedule or know who's out sick or what extras such as work trains they're going to run.

As a Conductor you have to be qualified on territory and as an Engineer you also have to be qualified on territory but also running qualified as in knowing your braking distances on these territories.

Here I am rambling.... you can hold whatever job your qualified to hold as long as your seniority permits.

By the way you start out at the bottom of the totem pole which is all the undesirable jobs

By the time your used to working on the railroad you'll forget what a holiday is or going to a birthday party or making plans for vacation.