I don't have an answer to solve your problem but I do think you uncovered a bug. See the 2 attached pictures.
I debugged your project to see if I could see what was going on and this is what I found:
I stretched the bottom left corner of the mesh to the left until it was nearly touching the left side of the screen. I then rotated it until the 2 left sides were aligned with each other. In the debugger, I took screenshots of the oleft and sprite2(0).x values.
The first image shows the x coordinate of the Sprite2 object on the far left side which should be your sprites bboxleft value. The second image shows the the value that was stored in the oleft variable. This should be the same as the first value but they definitely aren't. I am not an expert with the mesh object but from all I can see, your events should work fine, the system is just not getting the correct bounding box values from a mesh that has been deformed and then rotated.
I would suggest you submit this as a bug.