http://alivemod.com/forum/1142-putting-opcom-to-bed-on-empty-server

Final solution used by the author was

["someId", "onPlayerConnected", {
	if (({isPlayer _x} count playableUnits) > 0 || OPCOM_TOGGLE) then { ["ALIVE_SYS_PROFILE", "ALIVE_MIL_OPCOM", and "ALIVE_AMB_CIV_POPULATION"] call ALiVE_fnc_unPauseModule; OPCOM_TOGGLE = false; };
}] call BIS_fnc_addStackedEventHandler;

["someId", "onPlayerDisconnected", {
	if ( ({isPlayer _x} count playableUnits) == 0 ) then { ["ALIVE_SYS_PROFILE", "ALIVE_MIL_OPCOM", and "ALIVE_AMB_CIV_POPULATION"] call ALiVE_fnc_pauseModule; OPCOM_TOGGLE = true; };
}] call BIS_fnc_addStackedEventHandler;