no catch?

[Robert Goodman]

The catch is made and the ball becomes dead when the player on defense touches out of bounds. The only way that player could secure possession for his team would be if he were the last one in sole possession before going out of bounds. Otherwise the last team on offense retains possession.

You don't need solo possession for a catch. The loose ball is not extended until the player touches out of bounds, just because possession is simultaneous. If they break the plane of a goal line with the ball together, it's a touchdown if it's the attacking team's goal line, not a touchback.