What is the limit of Lovers Leap?

Two new champions have been announced in LoL.

They have an ability that makes them be able to recall together.

What are the limits to this ability? Can the 'non-recaller' jump in at the last second and get some kind of instant recall?

Can somebody with the setup to get on PBE test it and tell us what are the limitations of this ability?

I tested this on the PBE last night. Based on my tests, the only limiting factor in whether you can join the recall is your ping.

Contrary to what it may look like, simply walking up to the recalling player (referred to as the recaller) is not enough to join the recall. The recallee must also hit the Recall skill while in the small AoE indicator of the recaller. I assume this is to prevent accidental teleports from happening.

Because it takes some time for the recall command to travel from your own computer to the server, it might take a short while to join the recall. However, the recallee will join up as soon as the command is received. When I played yesterday, my ping was about 80, and I was able to join a recall with (approximately) half a second left before the warp happened.