Even if UEF had the proper equipment to manipulate magnetic bottles of Tev beams, I really doubt that they could pull off a beam deflection based only on "bending" over the magnetic bottle. I think the problem is in energy generation aboard UEF vessels: while Tevs are using extremely-efficient Meson reactors to create a proper magnetic environment for the beam not to "fart plasma" in the first place, the UEF seems to use more conventional reactors. If they would have a beam-grade energy generation capabilities, they would surely be using some more powerful plasma weapons (some huge, fast, stronk "blobs" at least) instead of all that munition-based cannons (I know mass drivers of any kinds, or UX Accelerators are powerful, but those torpedoes are still easy to intercept)
And I think this is why UEF is always going for enemy targeting systems instead of pushing the shots over with brute force: they don't have the brute force needed to do that. So they just use very sophisticated, low-energy EWAR systems in order to negate enemy advantages.
The best way of disrupting enemy beam weapons, except going for targeting systems, would be in my opinion: puncturing a magnetic bottle in a proper place to direct at least some of the energy outside of it, or pushing away from a friendly vessel the end of the bottle, let's say about five degrees. That's not much, but looking at UEF's capships' target profile, that might help push the beam away from vurneable parts of vessel to more armored regions (or into space if it's possible) if it's going too close to the hull.
Or we take a capacitor, store about 1.5x the (momentary) kinetic energy of the plasma in it, and when an enemy warship is powering up it's beam, just in the moment when it's pushing the plasma out of the emitter, we unload that capacitor through a stinger-like magnetic field right into that emitter, attempting to push the plasma back. If the timing is correct and we manage to get an advantage in the term of kinetic force just for a split second, the plasma does not even have a chance to leave the emitter, being pushed back instead. Since beam emitters are very delicate, I suppose the pressure buildup inside it will break something, make an overload ect. And boom - there goes a chunk of enemy warship, and the beam isn't even fired, so we do not need so much energy as deflecting the beam would require.
BTW - in HFH every time I left the Carthage in one piece in order to give the UEF some intel on Tev beams and some Meson reactors
