Robustness of voltage grid system or railway grid
Generally no. This is the sort of expected hazard the grid is designed to shrug off. Remember that it doesn't need a piece of wire to short circuit conductors either, an arc is effectively a short circuit, and you can get one of those provoked by a lightning strike, or tracking across a fallen branch.

It derives its resilience from a combination of current limiting, and over current disconnection. The generators and transformers feeding any section of line will have a designed impedance, such that the current resulting from a phase-to-phase, or a phase-to-ground fault will be ...

a) small enough that thermal effects and Lorentz forces will not damage in the time before disconnection, and 

b) big enough to operate over-current fuses or other types of circuit breaker fast enough to protect it

Bearing in mind a high voltage fault will often be an arc, and if you remove power from an arc it goes out, the first 'fault clearing' method tried by automatic switchgear is to interrupt the current for a short period, then reclose automatically. When you experience a 'brownout' in your home, that's the result of an adjacent link experiencing a short, and dragging your voltage down for the duration of the fault-clearing episode.