What are the grounds for refunding of Symmetra's teleporter?

Teleporters are refunded when either team's active spawn room changes. This is why you do not get a refund when the first point of Gibraltar is capped (neither team has spawn room changed), but you do for the subsequent checkpoints.

The amount of ultimate charge refunded is equal to [uses left]/6.

It might require further testing but from my experience there are 2 things to take into account :

• As @Lyrion said when you have placed a teleporter while defending point A, and the point is taken, you get the refund. This is likely to prevent your teammates from being teleported on the wrong location (and you getting yelled at by them ^^).

• The ultimate percent you receive seems to be based on the number of people who have used the teleporter. I had a game where 3 people had used my teleporter and I was refunded with 50% ultimate bar. This seems logical to me as the teleporter has 6 charges.

The only thing I don't know is if the proximity of the teleporter with the taken point is taken into account. It might need to be tested by placing a teleporter near point B, let point A be taken and see if the teleporter is refunded.