You complete a short course with 80 hours flying (and a bunch of simulator).
You are required to undergo a partner airline's multi-crew type rating course.
On completion of your line check, you are awarded a Multi-crew Pilot Licence, with the type endorsement you undertook.
At that point you may stay, leave or fly for any other operator - provided that you only fly multi-crew and only on a type on which you are endorsed. (i.e. you can apply for a job at another airline, but you have to complete a type rating on their aircraft, if they fly a different type - the same as any other license holder.)
Once you have completed 1500 hours, you may convert the license to a regular ATPL - exactly the same licence as any other ATPL holder. (i.e. If you now wish to fly single pilot under 5700kg, you would have to pass a BFR on under 5700kg etc).
Last edited by Checkboard; 4th Jun 2013 at 18:16.