As in most things in aviation, it is all about 'acceptable risk'..If an upwind engine fails on a heavy 747, just above V1, with a strong crosswind then the aircraft will probably not stay on the concrete. However, somebody has calculated that the chances of this happening are below ten to the power of seven, which is how 'acceptable risk' is defined in aviation.
When we used to fail engines on base training we always had to calculate the actual Vmcg, as we knew that an engine was going to fail. We still carry out three-engine ferry flights, where the CAA impose a 7kt crosswind limit from the side of the U/S engine for this reason. There is no limit from the downwind side.
On a lightweight take-off on a 747, the actual Vmcg is much lower than the published figure due to the derated thrust. However, if full power is used due to an MEL item then this can be a problem.
Airclues