England's RFU gave their approval to the agreement with 'Quins but the advantages and irony of using facilities so close to Twickenham will not be lost in the build-up.
"We've been really open with the Rugby Football Union," Cass said. "We talked to them before Harlequins and ourselves had an initial conversation. They are comfortable because we haven't portrayed it for something that it's not. It's an agreement with a club that's got a common sponsor and a strategic partnership to talk about how we might help each other from time to time."
Cass was keen to stress the shared Adidas connection played a major role in the groundbreaking agreement but it will also lead to players and coaches moving between the two countries.
"Both parties are dipping their toe in the water. Quite where it goes in terms of coaches, sharing ideas and looking at how we might get players from their academy down here to play some Mitre 10 rugby and vice versa ... those are the kind of discussions under way."
Relationships with clubs in other parts of the UK, Europe and Japan are expected to follow.
"Sitting down here at the bottom of the world, we've got to form relationships with clubs across the globe. Having some formal and informal links with clubs around the world is part of us doing business in the future. We've got to be open to those discussions - there's a lot of those going on now and they'll continue to happen."
New Zealand players taking sabbaticals at Harlequins and potentially other clubs to come raises the question of whether they would be available for All Blacks selection.
Cass, however, quickly shut down any notion of amendments being made to the policy of selecting only from within New Zealand.
"The policy is the policy. This agreement in no way changes that."
Former All Blacks captain Sean Fitzpatrick sits on the Harlequins board and Nick Evans, the Blues and All Blacks first five-eighth who enjoyed a storied career at the Stoop, were other key attractions to forging the first official deal with a foreign club.
"It certainly helps that we know Fitzy and we know he understands New Zealand rugby and Nick has been a great New Zealand rugby player and he's revered at the Harlequins club.
"Nick has been in New Zealand recently and we facilitated him being able to talk to a few coaches around the place. That's the kind of nature of how we see the agreement working."