So, A few have done it before, but also the information found here is unfortunately not up to date anymore so here is the latest one, from 3 days ago. Since I knew I would make a post about this, I took some pictures so at least you can visualize the whole thing once there.
At the main train station of Irkutsk:
you go to the right about 200m to these coordinates:
N 52°16.859
E 104°15.603
It's at the back of the building and at that point you should see this entrance:
Go in, you will see a few cashregisters and then turn left, 5 meters further you will see this door on your right:
Go in and on the left side there is a desk with two computers. (as you can see on the picture) One of the guy's called Rostislav and he's the one you need. His english is almost non-existent but he will use google translate with you to talk. He's really a good guy that will go out of his way to help you. He's the guy for the shipping of the bike, and he will also build the "crate" your bike needs to be in.
Rostislav is in the middle of this picture with the bike ready to be put on the train:
If you're lucky or if you have time you can get on the same train as the bike. For us this was unfortunately not possible so we had to take a train 2 days before the bikes. (high season, trains are rapidly full)
You pay by weight and the tank needs to be (nearly) empty and disconnect the battery. That's it. Paperwork is half an hour, and it's cheaper to put the bikes on the train than to drive them and an experience and more relaxing. Trying to figure out on what train you will be and on what train the bikes will be can take way longer.
Rostislav's details, I told him that I would make a post of this but please keep in mind he's 'just' a clerk and not the boss of the company or anything before calling/texting or mailing him. If you call or text do it with a Russian number so he doesn't have to pay for receiving it!
Rostislav Vetrov
phone: 89041260772
email: ROSTHELP <<{AAATT}>> MAIL <{DDOOTT}> RU
the company is
www.fpclog.ru