If you have a package, you are supposed to implement the IVsHierarchy interface. When you do so, you must implement the AdviseHiearchyEvents method. In this method, you must add the passed in sink to a collection you keep, something like this:

    int IVsUIHierarchy.AdviseHierarchyEvents(IVsHierarchyEvents eventSink, out uint cookie)
    {
        cookie = _sinkCookie++; // come up with some unique cookie
        _eventSinks.Add(cookie, eventSink); // remember this sink
        return VSConstants.S_OK;
    }

    int IVsUIHierarchy.UnadviseHierarchyEvents(uint cookie)
    {
        _eventSinks.Remove(cookie);
        return VSConstants.S_OK;
    }

And now, you can raise property changed events when you need, like this:

    private void NotifySccChange()
    {
        foreach (sink in _eventSinks)
        {
            try
            {

                sink.OnPropertyChanged(MyId, (int)__VSHPROPID.VSHPROPID_StateIconIndex, 0);
            }
            catch (Exception e)
            {
                SinkIsDead(sink);
            }
        }
    }