Tile over Luan which is glued to a cement floor
Can you do it: yes.  Will it come back to bite you:  probably yes.
Trapping wood between two cement building layers, in my opinion is asking for problems. 
If there is any moisture wicking through that cement slab it will be trapped beneath your tile in the wood - 
Do the work and scrape that floor.  I have spent days scraping a floor to prep for tile properly.  It is worth it knowing that I will not get a call back in 5 years.