The problems with gauge changing equipment is that it is very expensive and might not be satisfactory for use on heavy freight equipment. The only places in the World where automatic gauge-changing equipment is used is on a handful of passenger lines in Europe, especially on trains running between France and Spain (Spain is gradually converting its broad-gauge track to standard gauge). Elsewise, gauge-changing is accomplished by physically changing out the wheelsets/'bogies' on the equipment or by transloading the freight, a slow and laborious process. Also, the couplers between North America and China vs. Russia are completely incompatible.
As for dual-gauge track, the difference in the two systems' track gauges is about as insidious as it can get - 85 mm. They are too far apart for equipment to be able to run directly between each other and too close to allow for the easy creation of dual-gauge track by simply laying a third running rail. Dual-gauge facilities would require either 'gauntleted' four running rail dual-gauge track or building completely separate grades.
Mike, they're called "trucks", and you can use trucks that can go between 4'8-1/2" and 5' track. It's still a difference of 3-3/4". Split in half, that's still 1-7/8" between the two sets of rails. More than enough to use a set of trucks that works between the two systems. IIRC, they use similar truck in Europe already.
In addition, if the main route is to go between the US and China, Russia may (that's may, not will) agree to 4' 8-1/2" track between the two if that's where the line will go and have a yard for changing out the trucks further inland, nearer the Trans-Siberian Railway. Either that, or we have a yard near Fairbanks that changes out the trucks, and we build a 5' line from there to Russia.
Railroad axles that are gauged about 40-50 mm wide will likely at least derail at switches and crossings ('diamonds') here in North America, their tolerances are probably not that generous. In fact, I don't think that they'd fit between the existing 1435 mm rails, or if they did, the fit would be very, very snug and such equipment would be unreliable in its operation.
That would be a good question to ask in the professional rail forvms.
BTW, I am active in several very busy international forvms and in many instances, I am much more comfortable conversing in the terms that are normally used therein - most of the other forvmers, including the non-native English speakers in them, are then best able to understand what I am saying - with one big exception being that I still call them 'railROADs' (USA usage), not 'railWAYs', as is normally used everywhere else in the English-speaking World, including Canada.
Also also, quite a lot of the equipment that crosses the France-Spain border, especially Talgo-designed stuff, does not use trucks or 'bogies' - they use single-axle wheelsets that are individually attached to the car bodies.