heh heh, you won't find many B&Bs in Russia, if by B&B you mean quaint & cozy places to stay with a smiling proprietors. If on the other hand you are just looking for an adequate hotel (in the cities) or a rough & tumble truck stop (along the road) you shouldn't have a problem.
At least as far east as Chita, the major cities in Siberia are generally only a day's ride apart and you and stay in cities (Chita, Ulan Ude, Irkutsk, Krasnoyarsk, Novosibirsk, Omsk, etc.) if you want. If you want to stay along the road there seem to be quite a few truck stops of varying quality.
I have not been east of Chita but imagine that there are truck stops there as well.