Hi,
If I understood your requirement what you can try to do is to ask for a deferral (
http://msdn.microsoft.com/en-us/library/windows/apps/windows.applicationmodel.background.ibackgroundtaskinstance.getdeferral ), then connect to Lightstreamer in the asynchronous call and never return it.
Just pay attention to not keep too many deferrals pending.
Give it a try and let us know how it goes.