If the master electrician determines that Hydro-Québec equipment is at fault, he or she will notify Hydro-Québec and you will have nothing to pay.
If the master electrician finds your electrical installation to be at fault, he or she will estimate the work required and you will be responsible for the cost of repair.
In all cases:
Turn off any electrical appliances that were on, to prevent them from coming back on when the power is restored.
Unplug all your computers and other electronics to prevent damage from possible voltage surges when the power comes back on. This is especially important if they are not protected by a surge suppressor.