I would guess by now they all at least know someone who could handle any Dorico work submitted for them. Back in the 00s when NYC Boosey and Schirmer were both using SCORE or Sib in-house, I would occasionally get thrown some Finale work if that’s how it was submitted and they didn’t want to re-engrave.
Alfred and MakeMusic of course have the same parent company now, so I would assume they are using Finale in-house, but probably are capable of receiving things in just about any format.
Schirmer’s house style manual is available for sale. I’m an edition behind and have the 3rd, not the 4th, but it’s certainly a useful guide:
It was more of a general question. But in my present case, it is a catalog of (original) pop music scored for about grade 2 or 3 string orchestra. We did that work a decade ago in Finale in support of a series of clinics, but now there is some interest in publishing it.