[HvG Community]

https://forums.alliedmods.net/showthread.php?t=234863

Above one seem to work and you can then try something like this:

//Your plugin (Hook round start)

public void Event_RoundStart(Event event, const char[] name, bool dontBroadcast) 
{ 
    if(GameRules_GetProp("m_bWarmupPeriod") == 1) 
        {
            ServerCommand("sm plugins load noscope.smx")
           }
    if(GameRules_GetProp("m_bWarmupPeriod") == 0)
        { 
            ServerCommand("sm plugins unload noscope.smx")
        }
}