Sewer backup or any kind of flood is one of my worse nightmares as a homeowner. Well I guess fire would be the actual worse nightmare. I wish check valves were standard but they arn't. Check valves would solve a lot of these issues. Only danger is if it's raining too, then your weeping tiles have nowhere to drain to but if I had to pick between getting flooded with dirty water or clean water I'll take the clean water. Can always have a sump pump for that too.
One of these days I want to dig a new sump pit near where my sewer line exits, so I can add a check valve (with access to it from sump pit) and also put in a sump pump. Not really sure where you actually make the sump pump exit though... I doubt the city would let you send it to the street. I guess in a dire situation you do what you have to do. Fuck the fines. Deal with those later. Could just have a bunch of piping setup and ready to go so you can hook it up real quick to the house exit point and have it go to a storm drain or something.