Not sure of that. One example can be, if a Chinese client's account is full of USD, he would prefer to buy Russian things using USD avoiding the exchange charge and rate fluctuation even though the central banks have enough Rubel, RMB and EURO to facilitate the trade between the two countries.
So totally replace USD is not preferable so long as China have a large portion of its trade paid in USD. It would be a process of decreasing the portion of USD in China's world trade and Russia's increase on RMB. The reason for the later is that for a trader, Russian or Chinese, they want the most convenient and popular currency to buy things not only in the two countries but the rest of the world (except USA of course). That currency is more likely RMB than Rubel.
Therefor, my view is that establishing a technical system is the easy part, switching everybody's bank account and purchasing practice takes much longer time and effort.