I too have faced this problem sometimes. Evenif there is a column on which a partition is defined, is used in a range query, the partition elimination doesn't occur.
Is there any specific guidelines that should be followed while coding a query that should use the partition elimination ?
Do you get hte issue with pruning only when using subqueries in the filtering criteria or it's happening even using constant values for the filtering in the query?
For me it's happening in the first case and not in the second.
No timezone specification in my DDL.