The rule of thumb for mileage accrual within the Star Alliance (including UA) is that mileage earned usually depends on the booking class of the operating carrier.

Making things even more confusing, a United K fare purchased on a codeshare may book into some other booking class. So —
(1) Call LX and ask them what booking class you actually have on THEIR view of the reservation (it may or may not be K) (or check your reservation online on swiss.com)
(2) Look up the united.com earning for Swiss in the fare class you have on the operating carrier, http://www.united.com/CMS/en-US/Mark...spx?ItemId=297 per notes above
(3) You're done!

With other airline alliances, mileage accrual is a lot more complicated to figure out — the "marketing carrier" can matter a lot for figuring out how many status miles you've earned in the AA or BA systems, for example. With UA, usually only the operating carrier matters for PQM.