These things matter, notwithstanding the potential for  barbs to be thrown from Mulroneys detractors.  The former PM has likely been a stalwart mentor to PM Trudeau in the matter of US Canada relations.. He needs this and so does Canada.  

To Trudeau's credit he is handling the US file very well, in large measure because he is receptive to sound advice, some of which has come from Mr Mulroney.  Job well done.