Indeed, some obligations apply to federal institutions when third parties act on their behalf. Tourism B.C. is a good example, because it does not act on behalf of the Canadian Tourism Commission, for instance. They are two separate entities. There is no agreement between these two parties.
Some recommendations have to do with third parties. In the annex you will find obligations which apply when third parties act on behalf of VANOC. The recommendation was to the effect that the provision on obligations applying to third parties was not forceful enough.
There are also obligations which apply to sponsors that are not third parties. The recommendation you mentioned does aim to ensure that when there are agreements with national sponsors, there is indeed a language clause, to ensure advertising be done in both official languages.