This page agrees:
http://f22.aaa.livedoor.jp/~erel/rs3arrange.html
Also, if you check out the obi scan available on the album page, only Taro Iwashiro is listed as arranger.
As for the vocalists, I've seen 絵馬優子 romanized as "Yuhko Ema" (from her role as Fantine in the Japanese Les Miserables recording), though I prefer "Yuko" anyway.
Good job!