All I can think of is a rather terrible workaround.
Limitations include really fast balls not registering properly (because they've bounced off and are not overlapping anymore) and slightly inaccurate detection.
Here's the capx.
In short, I moved a set of 8 hit detection sprites to stay on the tiles surrounding the ball. When the ball hits the tilemap, it erases the tiles the hit detectors were on at that point.