I believe the Maus had two prototypes completed, one was sent to Berlin, the other was captured by the Russians. The former broke down about halfway there and had to be scuttled by the crew.
why scuttled?
pile up dirt on the sides and you have an instant bunker fortress
It was too heavy to transport by train I assume. Going long distances with tanks is begging for mechanical failures. And it probably broke down in the middle of the road which is why turning it into a bunker wasn't bright, plus the value of the machinery was probably too high to just 'leave it there'
Do you honestly think a maus would NEED a bridge to cross a river?
Considering the fact that a lot of modern tanks can't just go across rivers without preparations (ie snorkel and what not) unless it's a ford. It's a very risky adventure also because you don't know what's in the water, even if a recce crew actually took the time of waddling through the water to make sure it isn't either too deep or has a huge hole of doom in the middle of it's not a safe thing to do. Quite a few guys botch the job because waddling through the water isn't fun, or they can't notice some problematic things like ground that is rocky and good enough for a man but that would still let a tank slide into the water. Depth is also a problem. As a rule of thumb, water above the turret ring isn't good without fording preparations.
Another issue with fording rivers with armored vehicle is that the banks are usually where things go wrong. The ground is often very soft due to erosion and even if one or two tanks pass, the next ones might not be able to because the bank is non-existent anymore and instead there's a step to take.
Even the modern LAV's have issues with fording. Even though it's usually easier (because some models are amphibious and they require less preparation).
And finally all the ideal fording points are ambush points. If you're crossing a ford you're likely to be on the offensive (otherwise sappers would have prepared some sort of bridge, fixed the destroyed ones or you would have the time to go to an actual bridge). Enemies, if they did their recce correctly, know about those points. And they'll expect you to try and find them (and use them) because it's slightly better than a bridge because you can have infantry actually waddle through the river far on the flanks and do a box around the fording point, clearing it out of enemy.
