Thanks. I guess I just needed a little more patience. I finally found the following:

If a column is referenced in a subquery that does not exist in the table referenced by the subquery's FROM clause, but exists in a table referenced by the outer query's FROM clause, the query executes without error. SQL Server implicitly qualifies the column in the subquery with the table name in the outer query.

from:

http://msdn.microsoft.com/en-us/library/ms178050(v=SQL.90).aspx