They changed it in a patch, now "Zombie" state lose all his buffs and debuffs.

i Could not find the patch, i looked [here][1] but the last patch listed is from shyv (2011-10-31) 

[here][2] a post that has similar question

What happen now is only the increase speed per time from his pasive. but Ghost instantly vanish from the bar.

PS: I don't know if this is a bug or not (because i could not find the patch), but it is how works now (2012-02-26) at least.


  [1]: http://na.leagueoflegends.com/news/release-notes
  [2]: http://gaming.stackexchange.com/questions/51995/does-shurelyas-reverie-work-on-dead-or-decoy-champions