Webster refers to an OED reference to 'timely' being used adverbally, but deprecates it thus:
I'm surprised to find that my Shorter OED lists "timely" as an adverb also, and gives an example similar to yours: "They seemed to move the Socialists slightly, but timely, to the Right" (meaning "at the right time" or "soon enough" or "in time"). I do agree with you, though, that this usage is odd and people who use "timely" in this manner are not to be trusted. Leave your ear alone.
Looking at my Compact OED, and AskOxford.com merely draws a blank. My Fowler is at home.
Timely as an adverb strikes a dischord, but the meaning is entirely clear and the alternatives are clumsy.
Discuss.
