MBROverlaps(g1, g2)

Two geometries spatially overlap if they intersect and their
intersection results in a geometry of the same dimension but not equal
to either of the given geometries.

This function returns 1 or 0 to indicate whether the minimum bounding
rectangles of the two geometries g1 and g2 overlap.

URL: http://dev.mysql.com/doc/refman/5.5/en/spatial-relation-functions-mbr.html

