synergy543: Poser exports this material file for a single material object.

newmtl Preview
Ns 10
Ka 0 0 0
Kd 0.980392 0.105882 0.00784314
Ks 1 1 1
map_Kd pla001.jpg
map_Bump  pla001b.jpg

In Poser and Cinema4D the transparency for the ivy has to be set up 'by hand'.

Not fully sure but I don't think .mtl files are good with transparency. Seems easier to make and save new materials in the software being and apply as and when needed.