I agree with Robusto, I think. There is a semantic difference between "allow" and "allow for". "B did X, allowing Y" implies that by doing X, B directly caused Y to happen. However, "B did X, allowing for Y" implies that doing X may or may not, in fact, actually cause Y; Y may happen with or without X, or Y may require something else to happen besides or in addition to X.
Short non-sequitur, but consider a sentence in the context of carpentry. "He spaced the boards a quarter-inch from the wall, allowing expansion". Those who know carpentry know that you don't "allow" boards to expand; they simply swell and shrink with temperature and humidity regardless of what you do. Instead, you must "allow for" the boards to expand by taking an action ensuring that WHEN they expand, there is no adverse consequence. So, the correct statement, in context, is "He spaced the boards a quarter-inch from the wall, allowing for expansion".
Back to your OP, "a ceasefire allowing talks" implies that talks will not happen without a ceasefire happening first. "A ceasefire allowing for talks" may imply that talks are already happening, or that they could happen regardless of a ceasefire, but that the ceasefire facilitates those talks. Either may be correct, depending on the situation being described.
So, "allow" denotes permission, and thus a direct cause/effect. "Allow for" denotes either facilitation or "proaction" in anticipation of, and thus breaks the direct cause/effect relationship.
They are both correct: they elide the beginnings of different responses.
What does the door do? [What the door does is] close.
What does the door do? [The door] closes.
If you look at the verb be, you find that the former phrasing seems to be more productive and natural, if not necessarily more correct. Using the infinitive mirrors the structure of the question.
What does the Pope do? [What the Pope does is] be Catholic.
What does the Pope do? [The Pope] is Catholic.
I asked a question about this once that may be interesting.
Best Answer
Well, I don't know what you are getting at, but the sentence by itself doesn't make any sense. For one, "routes" are not machines and don't get old or stop functioning overtime, specially in today's world. Even if they do, the word "still" makes the sentence non-standard. Coming back to whether "functioning" or "functional" is correct, they both could be correct in a proper context. If it were a machine, I could say: