FYI....
From my understanding, using Multiprovider Hint table - OLAP reads the dimension table of where 0FISCALYEAR in each cube under this multi provider and then only it decides where exactly the user request based on year to go which cube - more standard way of course..
But the customer exit variable on 0INFOPROV will simply follows our own logic sometime more better- like custom control table or fixed cube naming convention like cube name with year.etc..etc...
Regards,
Arun