I can't imagine many too many cases where they'd be useful in everyday situations because if the car can't handle everyday situations then it's not going to be a good car and is going to sink to the "we're concerned for safety" lobbying that rivals will engage in to ban it off the road until they've caught up. Perhaps QR-code machine readable parking with the available hours, that'd be useful even without self-driving cars.
The purpose of most signage and road lines is to decrease ambiguity (Are there three or four lanes here? Which is better for a left turn?) and increase throughput safely. If signage could be made less ambiguous in such a way that self driving cars benefit, that's a good thing.
I think, however, that such a scheme should be based on single point of truth, ie. no QR-codes: The signage that a human can read should be the same that the computer can read.
The car knows where it is to within a few cm. No need for anything except a database of parking information. Don't clutter up the environment with QR codes that humans can't read.
I think, however, that such a scheme should be based on single point of truth, ie. no QR-codes: The signage that a human can read should be the same that the computer can read.