It seems to me that you never went to Uruguay by Entre Rios, the queue of trucks is ENORMOUS, because it is indeed very fluent the traffic between Arg and Uru. Also lots of Brazilians that come to Arg by Uru or even the traffic between Chile and Bra and Uru goes for Entre Rios.
And just the argentine tourist demand on summers was the leitmotiv to build a 350 kms highway between Colonia and Punta del Este, cause the rest of the year is empty, especially the 200kms between Colonia and Montevideo.
So if only this vacation demand made that route, it perfectly can make a smaller work as it is the bridge.
I dont like the bridge. I preffer things how they are. But if its done the bridge will be a success, no doubt of that.