If someone wants that bike that's shackled to the cart, they'll just ride off on it, cart and all. They may even throw their groceries in it too. Or cut the softish metal on the cart where the bike locks goes through in a Nu Yawk Minute.
There is no bike security, there's only better or worse security. I always park in an area like a grocery store or something that has people going in and out. Yes, those places are getting harder and harder to find, but if they close the grocery stores we will have bigger issues than having our bike stolen.
And I agree 100% w/ the locksmith, there isn't a lock made that a power grinder can't cut off in 30 seconds. I've seen it done. I would think a GPS device tracker could be easily defeated too.