I gave a partial answer to it in my response to Ms. Ashton's question.
It's important to realize that there have previously been federal-provincial agreements that have included language clauses. There is nothing new about it.
The federal government sends a very strong message to the provinces about the importance of official languages when it includes these language clauses and drafts the agreements in both official languages.
It also involves addressing the needs of official language minority communities. In the absence of language clauses like these, it's easy for people to forget about them in the process of drawing up an agreement.