i so you go after them if your old boses company is doing a piss poor job.
if they know you for your quality they will most likly switch over to you. do not wait till next season as they might be looking for someone else during the winter.
i view it as you would have never worked for him. if the company does a piss poor job next door i will try to get them as a client. if the workers don't speak a dime of English i will try to get them as a client. as well as everyone else on that street.
it is our eventual goal to get as many clients with the best roi on marketing.
we know every client will at some point leave us. try to get as many of those 120 to leave your previous bosses hands as possible. if he does a bad job now they will leave. if its a good job they will stay. worry about growing your business as much as possible, and not his declining business.
as for getting in trouble with the law ect. there is nothing to worry about.
one of my managers right now came from brickman, and another from a larger local company. both managers brought me there entire client list, it was part of there sign on bonus. we got lots of clients that switch when they heard the managers that they dealt with were leaving. and plenty of others from the other managers as well.