Not that I know of.

The only one is from ARIS to K2 (http://www.k2thought.com/?p=34)

You could try to reverse engineer it and do the reverse mapping but I think it would be quite a bit of work.

I think the other reason nobody has done it before is that

1. 
   
2. There is quite a number of features in K2 which isn't easily translatable to a BPEL format. 
   
3. Most people choose to stick with K2 on the workflow portion.
   

thanks for your answer