An ambulance chaser usually refers to a sort of lawyer who goes to accident scenes or hospitals to try to get an injured person to hire them. These type if lawyers are often held in low regard. The author here is using the same phrase to express contempt for the engineering consultants.

In it's literal meaning, 'ambulance-chasers' are unscrupulous lawyers who make a living by convincing accident victims to sue the responsible people. They follow ambulances to hospitals and talk to the victims while they are vulnerable. It's illegal in the US. In this context, it refers to people who have bad business practice that takes advantage of moments of weakness or crisis to sell unnecessary services.

An ambulance chaser is usually a lawyer offering shoddy work to an accident victim in distress. The accident victim is not able to make an informed choice. By comparing re-engineering consultants to ambulance chasers, the expert ("he") strongly implies that re-engineering consultants are offering shoddy work to companies in distress. Supporting words for this interpretation - dismiss (hold in low regard), mere rubbish (shoddy) New Oxford American Dictionary ambulance chaser | ˈæmbjələns ˈtʃeɪsər | noun derogatory, chiefly North American a lawyer who specializes in bringing cases seeking damages for personal injury. ORIGIN late 19th century: from the reputation gained by certain lawyers for attending accidents and encouraging victims to sue.

I think of “ambulance chasing” differently. It’s about insensitively and aggressively searching for business. (Someone’s hurt. I’ll use it as an opportunity to get a client) It’s not that the work itself is unnecessary or shoddy. What puts the practice in low regard is that it too quickly puts people who are dealing with personal injuries and losses in a situation where they are thinking about financial compensation.