I don't think I have ever come across the use of "million" or "billion" in any scientific documentation I have read or written. I suspect they do come up in discussion of the ever-problematic units of volume, where there could be semi-legitimate discussion of millions or billions of cubic metres where the correct way of dealing with the problem is to talk about cubic kilometres. Only a cubic kilometre implies 1000 cubic metres to the uninformed, out by six orders of magnitude, and is thus capable of causing confusion to the scientifically illiterate.
"Billion" in Germany is now in common use as 10^9, but only in English. In German "Milliard" is 10^9, and "Billion" simply never comes up that I am aware of, but you are more likely to hear these in a business discussion than a scientific one.
Anyone using "billion" "trillion" etc. here had better be aware of the ambiguity and be prepared for their bid for some company or other to cost them 1000 times what they were hoping to pay.