Modern Vespa

I replaced my front break pads today and found this cut on the rubber cover of both break lines.
Is this normal wear and tear or should I address the issue somehow?

That's very disconcerting. Yes, remedy this issue immediately by replacing the cover with something more durable yet flexible

Is this MP3 driven regularly on rough roads or cobblestones?

It's used twice a week for highway driving, about 60km commute. I think it's the first time when the break pads are changed so no one noticed.

Hopefully it is only the sleeve/cover that is cut but make sure you check the brake lines themselves (all of them) very closely. Any damaged brake lines must be replaced without delay.

The reason for the cover is to avoid the brake lines from chafing against the metal bracket as well as to avoid damage from road debris.

If the bike left the factory like this then somebody in the quality control department is asleep at the wheel