Then, in the 2010 file, eval the formula of the "all" table by pressing
C-c C-c.
==>

It takes the km value from the 2009 file, but also puts the cursor
(point) into the 2009 file in front of the ID:

* 2009
#+TBLNAME: 2009
  :PROPERTIES:
  :ID:       -!-ea32e5b5-31ba-468e-8e31-3e0d09696bb0
  :END:
|-----+-------|
|  mm |    km |
|-----+-------|
| all | 946.8 |
|-----+-------|

-=-=-=-=-=-=-=-=-=-=-=-=-=- cut here -=-=-=-=-=-=-=-=-=-=-=-=-=-

I'd prefer if the point would stay in the 2010 file.

-- 
Karl Eichwalder