"Someone suggested asking people at work to throw treats at her, but wouldn't this be counter productive if she is barking and lunging at them? Should she be calm before she is given anything?"
No, because your aim is to create a positive association, you're not at that point rewarding good behaviour...have you seen a behaviourist rather than a trainer?
Anyway, to answer your OP.
It took about 6 months to realise he'd not be going back to the happy friendly dog he was before the behaviour issue happened and about another year before I realised that I'd probably never be able to walk him without managing him quite heavily (up till then I was still hoping that at some point he'd be non reactive enough to let him be off lead for parts of walks and things like that).
And yes, it's hard work, really hard work and I have considered giving up on him altogether several times.
He tries to attack dogs on sight, as in, if they're within his field of vision, humans who don't approach him or look at him are usually ok, cars are ok about 50 percent of the time...when they're not ok, they get barked and lunged at too.
He is however fine with us and anyone who he knows very well, well unless he's trying to get to a dog and then he'll redirect on to me. (He is muzzled when out though)
It's looking very much like I may have to have him PTS soon anyway, his behaviour is caused by pain from some medical issues, one of which is much worse currently and we're pretty much out of treatment options to try, so I'm currently (under vet's advice) waiting a few weeks to see if it's a temporary flare up or whether that's going to have to be the end of the road - I'm not willing to keep him going if he's always going to be in too much pain to do things like go for on lead walks, it's not fair on him.