Are there any guidelines or set of standards for pro bono legal work
in the countries of France, Germany, and the UK?

Background:
In the United States, the American Bar Association has guidelines for
Pro Bono legal work called ABA MODEL RULE 6.1. It can be found at this
URL: http://www.abanet.org/legalservices/probono/rule61.html

These are simply guidelines that each individual state may choose to
adopt, but ultimately, each state can create their own guidelines.
However, most states choose to simply adopt rule 6.1 into their own
individual state bar association guidebooks. Some US state bar
associations have completely different guidelines (NY, DC, CA)

So, my question is, are there any guidelines or standards for Pro Bono
work in the UK, France, or Germany? (Maybe something similar to ABA
Model 6.1 applicable to the respective country?) Also, are there any
international guidelines or standards for pro bono legal work?

This is just a free comment and not an answer to your question.

I don?t know how much these sites can help you since they are in German.
The first one is that of the forum established by the Deutcher
Anwaltsverein (German lawyers? association)  specifically to allow
discussion of different types of pro bono work.
The second site shows the title article on the subject from the
magazine of the Berlin lawyer?s association, and the third one is a
discussion of the subject.
Many websites of German law firms mention ?pro bono? activity, mostly
international firms with offices and partners in Germany, which have
increased greatly in number in recent years.
The last two sites are just examples of this.

http://www.anwaltsforum.de/forum/index.php?c=6&sid=500245e7a713ba6ecc2b20877f05c86b
http://www.berliner.anwaltsverein.de/Downloads/AW_02_05.pdf
http://www.advonet.info/ju2187.htm
http://www.allenovery.com/asp/general.asp?pageid=253&languageid=0&
http://www.lovells.com/Lovells/AboutLovells/ProBono/Involvement/Introduction.htm

I doubt that this will suggest an answer to your direct question about
a guideline or standard from the German Bar Association (Deutsche
Rechtsanwaltskammer), but I hope a view of scene will be of some help.