Don't know what this paper is on about, but these things are planned in 'expeditions' with return vehicles set in advance by joint (NASA, ESA, RKA commissions) , they don't negotiate 'ups' and 'downs' separately, call it a package, in terms of logistics, planning etc... it's a complete deal. There is no point or savings in bringing down a 2 crew TMA instead of 3 (in fact it'll worsen the mass distribution of the descent capsule!) So, McArthur can bet on coming back in 182 days in the same TMA that brought him there (although, the Russians may get an '+' in the ISS balance ledger, yes there is such a thing) btw Dr. Griffin just came back from negotiations in Moscow:
http://www.federalspace.ru/NewsDoSele.asp?NEWSID=1148 , no English text though.
as in
http://www.energia.ru/english/energia/news/news-2005/press_release_iss-13.html :
"...
* Approve of RSC Energia proposals on the mission of the next ISS-12 main expedition with a duration of 182 days in the period of October 1st, 2005 to April 1st, 2005 with the cargo traffic to the station provided by the Progress M-55 transport cargo vehicle in December 2005
..."
also see
http://www.spaceref.com/news/viewsr.html?pid=18223 , scroll all the way down.
Now, the next TMA 'crew transfer package' with its austronaut will probably cost NASA extra (negotiations pending?).
(aside, the Russians don't have as much leverage as many people seem to think, for one thing, NASA controls most of the station's power distribution and generation, orientation, stabilization, two-way comms via. TDRSS (the Russian comms channels are extremely bandwidth limited - a few ground stations only - and time limited), and telemetry downlink; in the worst case NASA can cut the power off to the Zvezda module, just kidding! it won't come to that, I hope

and I think the Russian space officials are working diligently with NASA w/o much antagonizm)
Sorry for the long screed, just my understanding of the situation.