There seems to be another very close to OpenTTD "clone" for tablets: http://www.tt-forums.net/viewtopic.php?f=2&t=68650&sid=d157eb54801f51ccee522174b103d088
At least world and handling seems similar. But it is full 3D.
I like it, but I find hard to believe it's a 100% project, I think it's based on OpenTTD.
Being full 3D, they are not really much benefit from it, just on vehicle turning. At least they should add smooth zoom levels.
You can follow vehicles on streetlevel. Well. it looks like the PS1 adaption of TTD, but still this is a vast improvement.
But the streets and everything would suggest that yhey have reused OpenTTD code. Which then would require to release the sourcecode ...
Interesting timing since (iirc) TTD is itself being remade for tablets.