I have never seen this happen. I see all sorts of things I might be temped to call bugs but no passing a bridge.

I have around 1600 hours of playing the game and I figure I have seen most of its little glitches but this one has escaped me.

Their intercepts always work better than yours, but that is no big deal.

What was your difficulty setting? VH produces some odd behaviors too. I think the game has been geared toward Normal and anything else will allow the AI some weird abilities.