They are indeed.
They get an MP3 with everything they should theoretically need. The problem I've had since I started writing for others is that I've found good readers won't necessarily bother with the recording; their reading is good enough that they can easily sight-read the score so that's what they do.
I suppose it's not too dissimilar to an actor getting a script for something that's been filmed before who doesn't watch the original film.
I'm going to assume from my limited experience that this isn't exactly an unusual situation as I've seen so many event/wedding bands whose horn sections are, ironically, soulless because it appears that they're happy to just play what's written on the score that they spend the entire show staring at.