Ok, I am probably way behind on this observation, but on Mirrorball's track Peace and Love, is that Eddie singing the last stint of lyrics:
I took it all
I took the oath
I took it all
Til I had most
I took what's left
I gave it breath
I had it all once
I gave it back

I know Eddie wrote the song and if had to say, I would definitely say this is Eddie singing, especially with the slight growl in the gave it back part.

yep

Did Eddie write the song? Or did he just write the part he sings?

I think it's the latter. Especially since the album notes have Ed's part in type and Neil's in hand writing.

That is a good question.
I was looking at a few Neil sites and they had Eddie credited.
I guess I'll have to dig out the album out look for myself.

It would be nice to see the guys start to cover some of these songs on the next tour

oh, definitely. The closest that I have come to seeing that was the VFC concert in Toledo. Neil did Act of Love. It was pretty sweet to say the least.
I would love to see them do a few songs from Mirrorball. And on the flip side of that, I would love to see Neil do a cover of a P/J song. I don't know, he would do a cool Crazy Mary. He could pull off both organ and guitar solos I bet. Just not at the same time.

they covered throw your hatred down once on the 06 tour and it sounded really good

*fixed

Neil wrote the song, Ed only wrote the lyrics that he sings.

well twice at bsb, and twice in australia. It did sound fucking good at the syd and adelaide shows, probably my fav song off mirrorball

sadly i remember the mtv news break 5 minutes before the hour about this back in the day. i remember it because they played the clip and (i think) Tabitha Soren said something to the effect that if you buy the album to hear ed sing- you've just heard all he sings on the whole album. it mentioned that ed had guest written on the new neil young teaming up with pearl jam album sans vedder. it was something like ed saying to the effect neil asked ed to contribute lyrics to that specific part of the song or something like that. it was a long time ago, so i can't remember the clip verbatim.

Red Mosquito is Song X's "baby brother."

The typed, Eddie-written lyrics in the booklet aren't sung to the letter, though. I wonder if Young wanted to change them a bit?

Eddie isn't known for his talent of "getting the lyrics right".