could well be:
-LS used to codeshare on the portugalia service back in the 90's, so will be a nice return for them
-LIS say MAN is underserved, and with a 2 weekly WW service, its easy to see why
-May be a pre-emptive strike, as EZY were rumoured for MAN along with the new Libson base, so strike the iron while its hot
-Good star connections, and then going the other way good connections onto Brazil/faro/Oporto
-TAP have been rumoured before, so could this time finally happen?