Does the lead official mirrors the successful 3-point signal of the trail?

Maybe
 

In a word......maybe.

It depends on where the shot originated. If it originated from the T primary, and the T had the try signal, there is no need for the L to echo the make.

If, however, the try came from the L primary, and the L had the attempt, both officials should signal the make.

This of course assumes a two person crew. In a three person crew, the L should not concern themselves with signaling a made 3 point attempt.

In short, L never mirrors T, but T should mirror L.

In addition, we've been told that L should drop the signal once T puts it up.