I suspect Neil probably knows the basics of reading music but I doubt very much whether he uses it these days.
From a lot of the things he says it seems to me he's too impatient for a start and also too caught up in the mystery of music to pay much attention to notation. I remember him saying he felt computers in the studio could be a distraction cos looking at a screen starts getting you into the science of music rather than simply using your ears.
Also, he pretty much taught himself to play guitar but never learned 'properly' as he didn't have the patience, preferring to write songs instead.
Finally, in the Something So Strong book it says Mark Hart scored the brass parts for 'Together Alone' and that Neil was impressed by his ability to read/write music.
It all depends on how you define it I guess.
From a piece of notation I can tell what key a song is in and I know which notes are which but I can't sight-read nor have I been able to grasp converting the timing properly, preferring to rely on ear. I certainly can't write music yet I don't feel its held me back, not in songwriting anyway. I have a basic knowledge of which notes & chords can be used in a certain key and through that I get by. I only feel limited when it comes to lead guitar playing as I've never really learned scales etc so I have to find my way around by ear generally.