Let me start by saying, I've had work done by Alpine before - siding and was very happy with their work.
I got a quote from Alpine to replace the shingles on our roof, some were missing and there was leaking in the bedroom. They sent out an inspector and gave a quote for the total job of 3500 + HST. I got a second quote for 3400 + HST. I went with Alpine because of previous experience and they could get the job done quickly - which was important as we were slated to get a lot of rain.
Job started ok, but I got a call while I was in a meeting saying there was an extra $800 to remove the shingle as there were multiple layers. caught on the hop and we needed the work done due to the leaking, I said no to 800 but agreed on 600.
The fact is if it wasn't raining and the roof wasn't leaking I would have said no - there is no way that a small roof reuqired an extra 25% more cost to remove extra shingles. The fact is I clearly stated I wanted the shingles removed as there were already multiple layers, the other estimator also clealy stated there were 3 layers of shingle. In my view and I'm in sales - this is Alpines problem they quoted and were supposedly on the roof to assess the job. If I provide quotes to my customers and came back and said hey you know I missed something, guess what my customers would say - tough luck we have a contract.
My advice to you is to make sure you have a firm commitment on the price including removal if dealing with Alpine unless you want an unpleasant surprise.
Would I recommend Alpine? - Probably not. It's tough, I was happy with the work, but not happy paying more to use Alpine, only to be asked to shell out over 20% more to remove extra layers of shingles that that were clearly part of the job.