The decision ultimately comes down to the Speaker of the Legislature and the Clerk of the legislature. They can give a group a recognized status.
Here are the rules as set down by the BC Constitution as it stands at the moment.
1 In this Act, "leader of a recognized political party" means a member of the Legislative Assembly other than the Premier or Leader of the Official Opposition, who is the leader in the Legislative Assembly of an affiliation of electors comprised in a political organization whose prime purpose is the fielding of candidates for election to the Legislative Assembly and that is represented in the Legislative Assembly by 4 or more members.Interesting thing is that there is a definition but no use of the definition in the constitution.
The Standing Orders are not help much either.
So what does history tell us? British parliamentary houses are very tradition and precedence driven. In the last nine elections only in 1991 did more than two parties win four or more seats. It generally has not been an issue in BC.
Some examples from the past. In 1995 the Speaker of the day recognized the new BC Reform caucus with 4 members and the two member PDA caucus. The PDA did not exist as a political party during the 1991 election and BC Reform only ran four candidates and took 0.18% of the vote. Neither one was a serious political force but both of them received recognized standing as caucuses.
I am not sure the status of the PDA and Reform after the 1996 election, but at the opening of the legislature in June of 1996 Jack Weisgerber and Gordon Wilson were accorded the status of party leaders'. Given the end of both caucuses through the sitting MLAs joining one side of the house or the other and Jack Weisgerber choosing to sit as an independent, the issue became moot.
On the other hand in 2001 the Speaker did not recognize the NDP as a party caucus even though the party elected two MLAs and had a very long history in BC. The rule was four and the speaker enforced the rule.
Four independents do not make a political party and that alone is a very good reason for the Speaker to say they will not be a recognized caucus. If they were all to join a party that ran candidates in 2009 such as BC Refed or Libertarians or the Work Less Party, there would be a good case for them to recognized but the Speaker could still say no.
Does it matter?
Being a recognized leader of a party gives you debate time in the legislature and some extra resources though there is nothing clearly laid out as to what those resources are. More representation on committees would be important if the BC Legislature actually had the committees meet.
Honestly, given how the BC Legislature works, having a recognized political party caucus makes little or no difference if you are not the government of the official opposition.
One small final point, when John Van Dongen was sitting as a BC Conservative he was a BC Conservative MLA and not an independent. Because he was not part of a recognized party caucus, some people referred to him as an independent that was a member of the BC Conservatives party, this is not correct and goes completely against the history and tradition of the BC Legislature.