At last, I am on holidays with some time to answer :
From Sokolov, "Le comabt de deux Empires" p.273-275,
From a draft note of the czar to Czatoryski, his polish adviser, for a mission to propose to the Poles to join an anti-napoleon coalition, which should provoke defection of the german states:
"On sait qu'il n'y a pas plus de 60.000 français en Allemagne. Etant attaqués par surprise, ayant perdu ses alliés, on peut espérer que le succès sera complet"
letter from the czar to Czatoryski 25th of December 1810:
"...D'une part 100.000 Russes, 50.000 Polonais, 50.000 prussiens, 30.000 Danois, qui peuvent être renforcés tout de suite par 100.000 autres Russes
D'autre part 46.000 Français en Allemagne, 14.000 en Hollande, 30.000 Saxons, 30.000 Bavarois, 20.000 Wurtembourgeois, 15.000 Westphaliens et autres Allemands.... Mais il est plus probable que l'exemple que donneront les Polonais sera suivi par les Allemands, et alors il ne restera que les 60.000 Français. Et si l'Autriche, moyennant les avantages qu'on lui offrira, entre en jeu, c'est encore 200.000 hommes contre Napoléon."
This could have been only a diplomatic speculation, in line with constant 18th century policy of the czars to have a pro-russian king elected, instead of a saxon one. The report of Czatoryski about polish feelings and firm Poniatowski reply will put an end to this scheme.
But according to the same book, p.282 sqq, concentration orders on western frontier of Russia were issued on 21 and 22th of January 1811.
By spring 1811, 17 russians infantry divisions out of 27 and 6 cavalry divisions out of 9 were concentrated on polish frontier.
Most interesting, and also pointed out by Lieven, is that 5 of the 9 infantry divisions of Army of Moldavia were sent to western frontier, although the war against Ottmans was at a peak.
Russia was fully aware of the french force, thanks to spionage at the Ministry of war : by the same spring 1811, following orders of reinforcement by Napoleon, only 72.500 french and german allies were present in whole Germany, while 300.000 were in Spain and 350.000 in garrisons in France, Italy, Holland, and regimental depots.
So russian concentration was not jusitified by any french offensive threat, and pre-dated it by a whole year at least.
This is only a small extract of the book (in french).