Afraid the JAA IR groundschool is of no benefit to the ATPL. Not only are most of the exams of a slightly broader syllabus at ATPL, even the one which is of the same syllabus in all three (CPL, IR and ATPL) (Human Performance & Limitations) does not count for either CPL or ATPL if sat for the IR. If you are considering a CPL after your IR (or anyone considering an IR after a CPL) then do the full ATPL groundschool in the first place, it saves you an awful lot of time and money.