I've not seen eZ3 on MS SQL, but if you wrote a connector, it might work. eZ currently supports mySQL, postgreSQL.
Other threads for reading:
http://ez.no/developer/ez_publish_3/forum/developer/how_to_connect_msaccess_database_ http://ez.no/developer/ez_publish_3/forum/general/oracle_support
I hope this helps
Tony
Tony Wood : twitter.com/tonywood
Vision with Technology
Experts in eZ Publish consulting & development