Blockchain integration for toll collection sounds like an interesting usecase. Only issue I see is the data privacy. With everything being on the public node, a lot of data gets exposed to common man which can be used maliciously used.
I have an understanding that pvt blockchains in secure networks are already in use. Some companies are using it and testing it in their secure environment. The final call will all comes down to the supporting cost of the infrastructure.
That's not a problem. With blockchain, we can encrypt to whichever level we want. The nodes can even be operated by the public. That's the beauty of blockchain.