Well we know that when black holes meet they merge. We’ve observed black hole mergers and know that they release a huge amount of energy as gravitational waves, which are pretty harmless unless you’re right there.

Also, it’s believed that x-rays would be emitted, but that isn’t because of the event horizons touching, which is what you originally asked, but from the interactions of the black holes’ accretion disks and other nearby matter with each other and with the complex gravitation on the region around two merging black holes.

But yes even those x-ray bursts would be highly collimated and would only effect a small region directly in their path.