No, you will not be able to play on Ultra with acceptable multiplayer FPS. Your CPU will bottleneck your card and even ignoring this fact, you still don't have enough horsepower for 60FPS or more. My laptop, which is now a paperweight, has 2 GTX 675Ms, which are each equivalent to a GTX 560 I believe (your Ti is a little more powerful than one of them), but 2 of them definitely have more horsepower than your GPU solution. When I used to play on my laptop, I would get 45-55FPS on 1920x1080 Ultra, so expect 35-40 with a GTX 560 Ti. On your lower resolution, add another 5-10FPS or so. I suppose that isn't horrible, but you'll want 60FPS for multiplayer as a minimum. You still won't achieve the FPS I mentioned though since your CPU will bottleneck your card.
I'll note that benchmarks for this game as misleading. They are for single-player scenarios, which will yield significantly higher average FPS than multiplayer, especially once the game has developed and the map has been ripped to shreds. Your CPU will be hard at work and your FPS will drop as the game goes on.