Is it reasonable to expect that they should have noticed the torn LCA bushings and not done the alignment?
It is reasonable to expect they should have noticed, but not unreasonable to realize everything will get noticed. I had my 72 Chevelle aligned once. The guy worked and worked on it trying to get the alignment right. Finally he kind of gave up and said it was the best he could do. I found out not long after the lower ball joints were shot, so got them replaced. He had never noticed an issue, which is about as odd as your situation.
This is doubly weird in that if shops in Israel are anything like the shops here, the mechanics get a higher percentage from add-on work (work which the car didn't come into the shop for, but was noticed as needing done by the mechanic). It only makes sense they bring this type of work up as they can make more money per hour on it than regular work.
Do I need to do a new alignment after replacing the bushing?
Anytime you change suspension parts, you should get your alignment done. If the worn bushings give an extra 3° on either side to make up for it (exaggeration), then when you get the new bushings put in it will throw things way out of whack. Maybe if you talk to the shop where the alignment was done at, you can tell them what the issue is. They may check the alignment or give you a new alignment at a discounted rate.