It isn't at all suprising that MS SQL has been gradually diverging from Sybase, the only surprise (to me) is that it's taken this long. When MS secured rights to the codebase and forked, they probably kept TDS (the underlying wire protocol) in the interest of getting a product out quickly. That meant that Sybase client libraries could access the early versions of SQL Server. MS probably left good enough alone while focusing on reworking the guts of the database, and are only now getting around to introducing incompatabilities innovations that require new client libraries.

In environments where ODBC isn't available, or if Sybase drivers aren't available, consider using freetds.