A little project I'm working on.

scoring_wip.sp

#include <sourcemod>
#include <sdktools>
#include <left4downtown>
#include <l4d2_direct>
#include <l4d2util>

stock SetVersusRoundInProgress(bool:inProgress)
{
  static Address:pRoundInProgress = Address_Null;
	if(pRoundInProgress == Address_Null)
	{
		new offset = L4D2Direct_GetCDirectorVersusModeOffset("m_bVersusRoundInProgress");
		if(offset == -1)
		{
			SetFailState("Failed to read CDirectorVersusMode::m_bVersusRoundInProgress offset");
		}
		pRoundInProgress = L4D2Direct_GetCDirectorVersusMode() + Address:offset;
	}
	StoreToAddress(pRoundInProgress, inProgress ? 1 : 0, NumberType_Int8);
}

public Action:OnEndVersusModeRound(bool:count_survivors)
{
	new campaignScores[2];
	new chapterScores[2];
	new bool:tiebreak = false;
	
	L4D2_GetVersusCampaignScores(campaignScores);
	
	chapterScores[0] = (campaignScores[0] * 2) + 1;
	chapterScores[1] = (campaignScores[1] * 2) + 2;
	
	
	ShowRoundEndScores(campaignScores[0],campaignScores[1],chapterScores[0],chapterScores[1],tiebreak);
	
	L4D2_SetVersusCampaignScores(campaignScores);
	
	L4D2Direct_DirectorEndScenario(5);
	SetVersusRoundInProgress(false);
	if(InSecondHalfOfRound() && L4D_IsMissionFinalMap())
	{
		FireMatchEndEvent(CalculateWinner(campaignScores[0], campaignScores[1]));
	}
	
	// Block invocation since we're implementing it ourselves
	return Plugin_Handled;
}

// Campaign score 1 (pre),
// Campaign score 2 (pre),
// Chapter score 1,
// Chapter score 2,
// Show tiebreak
ShowRoundEndScores(t1,t2,c1,c2,bool:tiebreak)
{
	new iTiebreak = tiebreak ? 1 : 0;
	new Handle:scoreKv = CreateKeyValues("scores");
	KvSetNum(scoreKv, "t1", t1);
	KvSetNum(scoreKv, "t2", t2);
	KvSetNum(scoreKv, "c1", c1);
	KvSetNum(scoreKv, "c2", c2);
	KvSetNum(scoreKv, "tiebreak", iTiebreak);

	for(new i = 1; i <= MaxClients; i++)
	{
		if(IsClientInGame(i) && !IsFakeClient(i))
		{
			ShowVGUIPanel(i, "fullscreen_vs_scoreboard", scoreKv);
		}
	}
}

// 0: tie
// 1: team 0/1
// 2: team 1/2
FireMatchEndEvent(winner)
{
	new Handle:event = CreateEvent("versus_match_finished", true);
	SetEventInt(event, "winners", winner);
	FireEvent(event);
}

stock CalculateWinner(score1, score2)
{
	// The disasm of valve's version of this calculation is pretty cute.
	// Possibly a compiler optimization.
	// I try to be a little more explicit but still efficient.
	
	new diff =  score1 - score2;
	if(diff > 0)
	{
		// score1 > score2 == winner 1
		return 1;
	} 
	else if (diff < 0)
	{
		// score2 > score 1 == winner 2
		return 2;
	}
	
	// score2 == score1 === winner 0
	return 0;
}