I don’t see much in there about not working alone. The section on it simply says “The following high risk activities that may be required during a fire investigation should be avoided when working alone:” and goes on to talk about specific situations. Even the situations are open to interpretation. How many fire investigations don’t involve working with electricity or tagged or locked out electricity? How many don’t involve hazardous substances or materials? I think the whole fire scene is full of such substances and materials. I don’t believe this language is either strong enough nor does it suggest that you should have someone with you. It also refers to ‘allowing’ for a buddy system, but again, allowing for something is different than recommending it or requiring it.
If I fall through a floor and my cellphone or radio lands away from me, I’m not sure how this guidance note is going to help save my life or get me prompt medical attention.
If I am alone on a fire investigation with hazards such as holes in floors or areas with compromised building integrity then I think that only a second person on site constitutes a safe working condition. Many times our fire suppression crews are cleared when we arrive or shortly after. Climbing ladders (especially if removing plywood from windows), working in an attic with joists only or other situations, it surely makes sense to have a second person with you.