How to play and read scales when the treble clef appears with the bass?

1. What is it called when the treble and bass clefs are put together?
2. Do bass players read treble clef?

What is it called when the treble and bass clefs are put together?

The grand staff (or “great stave” as it's called in Britain), is a combination of two staves put together, usually a treble clef and a bass clef.

Do bass players read treble clef?

Even though its a baritone, the music for bari is written in treble clef. Bass guitar is a C instrument and the music for it is written in bass clef. The instruments that you mention are transposing instruments, which means the music is written in a different pitch than concert pitch.