I actually was a Sybase ASE DBA for quite some time, too (spent a lot of time in the DBA trenches - Sybase ASE is my favorite SQL DBMS) and it's my understanding that SQL Server around the 2000/2005 mark was completely rewritten. Although the origins of T-SQL are Sybase, the rest of the product isn't (some of the philosophy and core architecture still is a carry-over from ASE).