All sanctioned events have to have a safety plan. See here for sanctioning info, including a sample safety plan. I've been to a few where there was indeed a truck or station with first aid available, but that's not always the case.
NOF rules, section 22.14 is about safety and "service" (toilets and babysitting, etc). (Google Translate will probably work ok.) Looks like the requirements for local events is just that there's a first aid kit available and that there's a way to communicate from the arena. As the events get bigger the requirements increase. And there always has to be a plan to search for people and be able to transport people, so that's sort of similar to the safety plan.
I made a quick search on the website for the Swedish federation but couldn´t find any written rules regarding this. There´s the occasional mention of 'safety plan' and 'first aid' but nothing specified where I looked.
My feeling is that this is still taken care of - maybe a little differently between organizers though. At our low key mid-week Veterans´ events there´s even a defibrillator available which is fine knowing the age of people that show up. It came to good use at another local event last fall which turned out to save a life :)