The OGC intent was certainly to permit subqueries, but there's still the SRID issue with
which to contend. A Microsoft forum would probably be a better place to find experts on
GEOMETRY behavior in SQL-Server 2008.
ArcSDE just uses an envelope search as a filter and then uses Esri's libraries for topological
comparison (whether it's GEOMETRY/GEOGRAPHY, ST_GEOMETRY, SDO_GEOMETRY,
PG_GEOMETRY , SDEBINARY, or SDELOB storage). Shape library comparisons are done at
the precision specified by the layer coordinate reference (inverse of xyscale).
- V