Inability to describe ResultSets returned by ProcedureQuery causes all kinds of issues. E.g. see this thread (Long vs Integer):
Check out 1.1.3 fix of this issue here: http://objectstyle.org/confluence/download/attachments/134/cayenne-1.1.3p1.jar?version=1
The fix for now is to allow setting result set column descriptors at the procedure query level (without Modeler support). This is how far we will go in 1.2...