Gullibell - I still don't see it - if that gear fails (not sure what you mean by gear failure - does it disintegrate or just stop spinning?) the gear that links it to the TR drive must surely also fail/stop spinning since it is attached to the same shaft (as far as I can see in the diagram).
And, if the gear fails and the load from the MRGB is suddenly removed leaving only the load of the TR on the No1 engine (especially in the cruise with relatively low TR thrust) there must be a Tq split until the N1 governor for No 1 engine catches up and backs off the fuel.