Since in the simutrans section pak96.comic was introduced, people asked, if it could be possible to reuse the graphics for OpenTTD comic set. Since Simutrans grf (pak) system is much much easier than OpenTTD grf system and furthermore the simutrans people are mostly simutrans only player, it was agreed that the simutrans community (i.e. Alexander Brose) provide the rescaled images but any work for incorporation into a grf-set must be done by the OpenTTD community.
The best way to get an idea of the graphics, would be to have a look at the simutrans sections pak96-topic (https://www.tt-forums.net/viewtopic.php?f=22&t=40304)
The following images have been converted to 64x64 pixel size (all copyright by Alexander Brose) and are just waiting for a coder.
Imho these building do not fit very well with the surrounding of the 8 bit OpenTTD graphics and woudl need some less dithered landscape too. (Again see the above link.)