We've been using 'go by' for years. I myself use it quite occasionally in the following context:

I'm looking forward to next weekend's party. It should be pretty good if last week's one was anything to go by.

Nah. It's not a new term. Been around for ages. Dubya heard it on the radio or read it in a book (whilst colouring in the pictures, presumably). Doubtless he has a special dialect adviser who looks up these words for him. Of course (and it's not unknown to happen), he may have misused it.