Environmental work often involves supervision. I’ve been watched/overseen by facility managers (who may or may not represent our client), regulators, and other consultants.
Subcontractor oversight is pretty simple because the relationship is spelled out in a contract. But when I do oversight of fellow geologists or consultants, I tend to have more of a co-worker relationship. I’ll speak up if I see something wrong, and if they disagree or ignore me, I’ll make a note of it, but I’m not out to get them. This is true even when our respective clients are adversaries.
I’ve only had one experience where another consultant was really aggressive and difficult. In that case, the owner of the consulting firm was a close personal friend to a property owner who was opposed to our investigation (and with reason – the investigation indicated that part of “our” contamination originated on “their” property). The consultant for the other side sat on the public road as close as they could get to us, just outside the safety zone we’d set up, and tried to intimidate me by taking pictures, questioning our methods, and generally being a big pain in the ass. We had other rigs working on the project, but they stuck to me because I was the least experienced geologist. They were clearly hoping to find some errors in what I was doing, or even to force a mistake by harassing me. They only left when the field manager showed up.
Now I have a lot more confidence, and I’m not afraid to tell people “I will NOT discuss this subject with you further. If you have further questions, you’ll need to contact my client representative (PR person) directly.” But in my experience, overly aggressive consultants are thankfully rare.