Found a few more details
Each MP level adds 25% MF, MP levels 1-3 add 10% exp each, 4-6 add 15% exp each, 7-9 add 20% exp each, and 10 adds 25%. The aggregate bonuses for +MF% and +exp% at MP 10 are therefore 250% and 160% respectively.
These are values in inferno and do break the 300% cap...