At the edge of available 45 degree imagery, it shows grey "no imagery" tiles instead of swapping back to regular imagery.

Maps.google.com properly swaps to regular imagery immediately, but the API doesn't.

Example code: http://lib.concept3d.com/reported/45_degree_imagery/

Scrolling left and right on that sample will give you an idea of how it behaves. It will finally swap to regular imagery when no 45 degree imagery is visible at all.

Thanks!