I don’t think you’ll get a cat expert stating outright that the Russian Blue is a lap cat. This is because you can’t brand all the cats of one cat breed lap cats. It is an individual trait. However in reference to one of the best books on cat breeds, Legacy of the Cat, I can say that the Russian Blue is a sweet, gentle and shy by nature domestic cat.
They make excellent loving and playful companions for their owners. They can be cautious with strangers. The author of this book, Gloria Stephens, goes on to state that cats of this breed are generally content to remain indoors and watch the world go by. They are sensitive cats and affectionate. They enjoy the company of their owners. They are receptive to playing games and being trained.
The general tenor of the description of this cat’s temperament indicates that, in general, they will be a lap cat. The caveat is that individual cats will have their own personal traits. You can’t really generalize across an entire breed unless we could argue that all Russian Blue cat breeders breed for character and temperament over appearance, which is not the case as far as I’m aware.
Perhaps the best thing to do is to go and talk to a Russian Blue cat breeder and meet the cats. Let the cats introduce themselves to you and you’ll see, possibly quite soon, whether one of the cats likes to be on your lap.