It's a non-nonsensical idea that an actual bridge would be built in real life in Stalingrad (historical map) and then be unusable by anything in game terms because a 'unit can't cross the bridge without a road hexside.' Clearly there is a problem with the map and/or the rules.
I don't think the rules should read as they are and it's another of example of the rules being written for brevity, whoever wrote them never imagined a bridge without a road crossing an exiting hexside. But here we have one! And why should the road depiction be required to cross the hexside; it's an arbitrary spacial construct after all.
The rule should say: Entrance of/exit from a bridge Location can occur only by crossing a road depiction from that bridge and if the road enters a hexside, by crossing that hexside. If the road depiction from the bridge does not cross a hexside, then units may exit the bridge visa bypass or normal movement to any hex that is on that side of the bridge (example, from the bridge in RB CC31; units can exit the bridge across the road hexside CC30 or by entering BB31, entering or bypassing CC31 or DD31) [a graphical example would be needed since not everyone has an RB map, soon to become more or less obsolete]
Note -- I think this situation can also occur when an artificial counter-form bridge is place, but in that case the edge of the counter conforms to a hexside, so units have to exit the counter from that hexside.
However, RB CC31 may be a truly unique example that's basically an artwork mistake, so some errata could be issued such that the road is extended through the hexside but not entering the building (so it's not considered to be an RB factory).
It will be interesting to see if this artwork is corrected in the upcoming release of Red Factories. That's the best way to solve this, perhaps.