Yes, there is no requirement or specifications of a scenario team.
There are in fact 2 recognised one man teams in the uk - Keams & Gommie
Meet them on or off the field of play and you will understand why
Other than the 2 individuals I am a member of what was the smallest UK team, especially if you count the original core of 2, but that was before we adopted a name.
You can form a scenario team just by deciding you are a team, but it helps to turn up and play for a game or two
On average a team will generally play walkons at their local site, (multiple teams in an area may play with/against each other at walkons) and play the scenario events they fancy. You do also get occasional 'invitationals' which could be a challenge or a bit of practice together
There are some teams that are national with members spread throughout themcountry and only get together at scenario events. These have formed from friendships born out of the events people met at.
There isn't an organised league in scenario but on occasion there have been links, there is a 'scenario Grand Prix' which maintains statistics, there is the UWL which is a woodland league, NPF run Diamond Wars which follows on the theme and score through their walkons and links into Paintfest
Some scenario teams play tournament paintball and some tournament players & teams play scenarios
With a scenario event you just buy your ticket, pick your side and play
It could be your first ever game, or you could be a 'pro player'