If a question asker clicks to be notified of answers by email, then someone migrates their question...
- Are they notified by email of the migration?
- Do they receive email notifications of answers on the new site if they aren't registered there?
You do not get a email about the migration but you do get a notice on the site.
Regrading about the new site if I am not registed you can link the two accounts and if you have more then 200 rep on one of them you get a 100 rep bonus.