That is not my experience with company cars at all - times really have changed. The last company I worked for had a fleet manager who was meticulous at making sure ALL the company cars were impeccably maintained. Servicing intervals were strictly adhered to, fitting anything other than manufacturer recommended tyres was a no-no given the fact that the lease company would charge back if the cars went off lease in anything less than excellent condition (i.e with junk rubber fitted etc).
In my eyes the fleet manager is responsible for everyone's safety, at least he was at my previous place. enfed up at auction The company (like many) wanted to run their fleet as economically as possible, but not at the expense of a law suit.
Ex-company car can be very good buy's, provided you do your due diligence.