I'm not sure I'm following.

If the calendars are in Global.mpt, you should not need to copy them to a brand new project - they should be in the list of calendars available in the Change Working Time command.

You are correct, task calendars do not appear to be part of the copied data. I'm not sure why you are copying and pasting data - can you use the "New from Existing File" to bring the tasks over to new file?

To speed up assigning the task calendars, drop the field into the view.