I didn't think that riding a bus was a public service since a fee must be paid.   But, anyway....

Religious freedom is not the same as religious accommodation.
The face is a special part of the body.  Our species, and probably others, use it to identify and assess temperament intuitively.  Have you ever experienced a baby gazing at your hands?  

If I access public services (paid for by my taxes), I expect to indulge in that human activity of looking at the face of the person(s) with whom I am interacting.  I have no obligation to accommodate someone else's religion.  If I was hiring someone to cut my lawn, I don't have to hire someone wearing a mask.  Why should I have to do it when I renew my driver's licence?

Religion aside, why do these people feel it is necessary to cover their face in public.  I know that there is some psychological condition that confines people to their houses.  Is this an extension of this?