Yes! Now it makes sense -- in the "sharp or astute" sense. I wish I could use it, but I don't think anyone around here would get it, then I'd have to explain it, then I'd sound all pretentious and end up taking a world of crap from my friends...again. Rats.
I do think it has a better nuance of meaning than that. I see 'minding' here as caring for, keeping safe, and maintaining order and control. Quite a feat at a crossroads, which conjures up an image of busy traffic movement in all directions, creating all manner of terror in the mice there.
I love this phrase - in spite of the fact that I think I don't know what it means... Does it mean that the person is at a crossroads, mice are directing traffic there, and the person obeys the mice? 'Cause that's what I think it means, but that doesn't sound particularly smart to me... help!