Well, about the car being a company car, is that what they told you, or do you have proof?
If it really was a company car, I wouldn't be as concerned as if it were to be a rental car. Rental cars get beat up on a lot. Company cars are harder to predict, because one can make a general assumption that someone who actually receives a company car is someone who is higher up in a company, hence more responsible and less likely to beat up on their car. Basically, if it's a company car, I'd say the chances of the car being beat up on is about the same as a car that has been previously owned by a private party.
But I would definitely do the carfax thing. In fact, a good dealership would be willing to supply the carfax report. Ask for one. 140,000 miles is a little high to not check out what kind of car you are getting.