Hello Roger,
you could build a script with a polling logic that:
a) issue show isdn status, parses its output
b) if L2 ISDN is fine does nothing else perform a shut/ no shut cycle
the correct state is :
a TEI assigned, state MULTIPLE_FRAME_ESTABLISHED
For example you could use EXPECT that is now included in activetcl at
www.activestate.com
or other scripting library of your choice
Hope to help
Giuseppe