Edit:23 nov. 2016, Cre:23 nov. 2016
It exists plastic buildings UV resistant in some reputed brands:
It exist German and American style buildings. The proposes models are not very realistic for other countries.
PIKO buildings while being presented as being at a scale of 1:22.5 are in fact much smaller and their real scale is from 1:29 to 1:32. They cannot be used as station building in a 1:22.5 network. They could be used as background buildings (with people at a scale 1:32) or as accessories buildings (cabins and utility buildings).
For other countries than Germany and USA, you may search local small manufacturers or you shall help yourself and build your models or adapt existing models.
AristoCraft had a small set of american style buildings ate a scale of 1:29.
POLA, PIKO and Faller buildings can be bought in Germany at modellbahnwelt24. You can communicate in english with them.
As Faller bought POLA and PIKO, there may be some merge of distribution network.