Challenge: Russian Tibet

With a POD no earlier than 1800, make Tibet become a part of the Russian Empire or a successor state (e.g. USSR). Bonus points for a union that lasts until the present day, and also for an otherwise territorially intact China.
 
On April Fools Day, 2012, Tibetan seperatists swear allegiance to the Russian Federation. A drunk Putin accepts their petition to become a Russian Republic. ICBM's fly.
 
With a POD no earlier than 1800, make Tibet become a part of the Russian Empire or a successor state (e.g. USSR). Bonus points for a union that lasts until the present day, and also for an otherwise territorially intact China.

I doubt Tibet could become part of Russia/USSR without Xinjiang also joining, since Tibet isn't close to bordering the USSR. Perhaps during the Chinese Civil War, the Soviets get greedy, and Stalin "offers" membership to any Chinese province (and perhaps to Mongolia as well). At the very best the USSR could snap up Mongolia, Xinjiang, Tibet, and maybe even Manchuria. China and the Western Allies would be highly displeased, though, so perhaps the Soviets would wait until they develop nuclear weapons in 1947. Xinjiang might be easier for the USSR to annex, since Tibet borders British India. You'd need a very ballsy Stalin to attempt this though. What remains of China, even if dominated by Communists, would certainly not be friendly with the Soviets at all.
 
How about a no Open Door Policy? While the other powers can't turn their areas of influence into colonies because their too heavily populated to control, Russia's area of influence was less populated and outside of China proper. While in Europe, Russia enters an alliance with Germany against France and Britain and then the two sides go to war and the Russian-German alliance is victorious and Russia manages to gain Tibet at the peace conference and intends to incorporate it into its empire.
 
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