SQL Server 2008 :: Partitioned Views Table Elimination Not Working

I have some Partitioned Views and on all queries using a table for the in clause, table elimination isn't happening.

Check Constraint is on the oid column

This works as expected, only goes to 2 tables;
SELECT *
FROM view_oap_all
WHERE oid IN ( '05231416529481', '06201479586431' )

This works as expected, only goes to 2 tables;
SELECT *
FROM view_oap_all
WHERE oid IN ( SELECT oid
FROM owners
WHERE oid IN ( '05231416529481', '06201479586431' ) )

This is checking all tables (headingnames are unique), ive tried this for the last 3 hours on many different tables containing the oid column.

Unless I write the oid as in the above queries it just doesn't work.
SELECT *
FROM view_oap_all
WHERE oid IN ( SELECT oid
FROM owners
WHERE headingname = 'TestSystem' )