There is a bug (?) with #+call block: They are not executed on export/
invocation of org-babel-execute buffer.

There are a couple of reasons for this:

   1. org-babel-src-block-regexp, used in org-babel-map-src-blocks
   	  does not match #+call.
   2. unlike org-babel-execute-maybe, which calls
      org-babel-lob-execute-maybe if org-babel-execute-src-block-maybe
      returns nil, org-babel-execute-buffer just calls
      org-babel-execute-src-block (there is no corresponding
      unconditional org-babel-lob-execute-src-block).

This seems to be an oversight.

tia,
rick