Based on the signs, I would recommend "CR-B15" as the format. There's no hyphen, and the sign says "County", and doesn't say "Highway". I think that's plenty clear enough.
TTS should say "County Road B Fifteen" for that.
Exits that share a milepost are designated with numbers, e.g., "Exit 235B". In my area, that's how they are displayed on the big green signs, and that's how they are on the Waze map as well: "Exit 235B: Canal St / Superdome". It is pronounced properly, as you might expect, "Exit Two Thirty-Five B, Canal Street, Superdome". I imagine it would work the same with the letter before the number, then.
Not sure about "PA-1", but I know that "LA-1" is prononuced as "L A One". As for the other letters, none of them stand for anything. Michigan smartly skips from D to F in their county road designations and stops before N, so we don't have to worry about any cardinal directions slipping into there.
TTS should say "County Road B Fifteen" for that.
Exits that share a milepost are designated with numbers, e.g., "Exit 235B". In my area, that's how they are displayed on the big green signs, and that's how they are on the Waze map as well: "Exit 235B: Canal St / Superdome". It is pronounced properly, as you might expect, "Exit Two Thirty-Five B, Canal Street, Superdome". I imagine it would work the same with the letter before the number, then.
Not sure about "PA-1", but I know that "LA-1" is prononuced as "L A One". As for the other letters, none of them stand for anything. Michigan smartly skips from D to F in their county road designations and stops before N, so we don't have to worry about any cardinal directions slipping into there.
Re: County Road Naming