[teame06]

This was only tested on CS:Source

#include <sourcemod>

/* Thanks to kzfi`p3tsku for this info. */

/* VGUIMenu Structure
BfWriteString(bf, "scores")
BfWriteByte(bf, 1)
BfWriteByte(bf, 0)
*/

new bool:IsIntermissionCalled;
new UserMsg:VGuiMenu;

public OnPluginStart()
{
    VGuiMenu = GetUserMessageId("VGUIMenu");
    HookUserMessage(VGuiMenu, _VGuiMenu);
}

public Action:_VGuiMenu(UserMsg:msg_id, Handle:bf, const players[], playersNum, bool:reliable, bool:init)
{
    if(IsIntermissionCalled)
    {
        return;
    }

    new String:Type[10];
    BfReadString(bf, Type, sizeof(Type));

    if(strcmp(Type, "scores", false) == 0)
    {
        if(BfReadByte(bf) == 1 && BfReadByte(bf) == 0)
        {
            IsIntermissionCalled = true;
            // Intermission?
            PrintToServer("Intermission");
        }
    }
}

public OnMapEnd()
{
    IsIntermissionCalled = false;
}

I would like to thank kzfi`p3tsku for this again.