I have in my lab a VLAN enforcement for Alcatel OnmiSwitch where as addition the Avenda-Tag-Id attribute is added with value of 0:
In case it doesn't work in your case you may try to add this attribute (or actually remove it if you read the following description: http://community.arubanetworks.com/t5/tkb/articleprintpage/tkb-id/Controller-lessWLANs/article-id/803
There should be guides available through Alcatel on how to configure their switches with ClearPass and it probably covers more advanced cases as well. I don't have those guides, so unfortunately cannot share them.