TromboneChat

Is anyone familiar with this arrangement?

Passacaglia and Fugue in C Minor
JSB arr. Eric Crees

It is scored for 5 trumpets (+flugelhorn) • 4 horns • 3 trombones • 3 tubas • timpani

I was wondering if one of the three (3) tuba parts could be played either by euphonium or bass trombone??

Depends on what your artistic/aesthetic goal is. Play the notes, yes. Match or closely approximate the sonority, probably not: a euph will likely lack the requisite weight and breadth of sound (particularly in the compensating and pedal registers) and a bass trombone has a different timbre.