They are bridge virtual interfaces VLAN based, so they are always up AFAIK (I mean they are independent from physical cable connection)
It depends on how it is configured. At least it used to be like that in the days of "master-port" and switch configuration. E.g. when you configure a VLAN with only some ports on it having that VLAN, and all of those ports are disconnected, the entire interface was down.
However with the migration to "bridge with VLAN filtering" I think this functionality may have been lost.