New to Authoring, have a basic subtitling question

Hello

I have to bid a job and was wondering a couple of things:

1. Can you add subtitles to a Blu-Ray project in Encore. (Thought I seen somewhere that you could not.)

2. What type of files should I use? I have authored with .STLs in DVDSP, and that's what my Captioning service provides. Should I ask for a different type of file from them instead? Or will Encore accept the STL file?

Any help on this would be appreciated greatly.

Thank You