The service will offer both free and paid content to everyone, not just Spark customers.
"Our agreement will broaden the availability of New Zealand's biggest sport and give viewers even more choice," Kenrick said.
"Together we're committed to delivering a fantastic viewing experience for all New Zealanders – making the most of Spark's leading digital technology and distribution capabilities and TVNZ's unrivalled audience reach and content expertise."
Fans will be able to stream games over a broadband or mobile connection via an app that can connect to TVs, laptops, tablets and phones.
Spark won't be releasing pricing details until next year. However, packages will include individual match passes.
Spark managing director Simon Moutter said its tournament coverage would be available to all, not just its customers. Rather than the "all or nothing" bundle previously used for Rugby World Cups, Spark intends to offer pricing options "to suit people's differing preferences and budgets".
"At Spark, we want to help shape the future of sports watching by New Zealanders, so we are immensely proud to be bringing these iconic tournaments via modern streaming capabilities that offer a richer, more engaging viewing experience. We intend to use the power of technology to give Kiwis more control and better choices about what they watch, when they watch and how they watch."
This announcement comes off the back of news over the weekend that the Commonwealth Games airing on TVNZ were more popular among Kiwi viewers than the 2016 Rio Olympics, which aired on Sky.
The broadcaster said Nielsen data showed that with three days of the games to go it had reached 2,746,800 New Zealanders, compared to 2,651,800 for the Rio Olympics across Sky TV's main sports channels and Prime (excluding pop-up channels).
TVNZ has certainly been helped by a more forgiving timezone, but it has been pushed as an indication of the strength of free-to-air broadcasts.
However, the full benefit of free-to-air will not be realised during the Rugby World Cup in that only seven games will be aired free on TVNZ.
In a recent interview with the Herald, Sky director of sport Richard Last suggested that Sky would've been hesitant to put the tournament behind a digital paywall, given the fact that so much of the nation continues to rely on broadcast television.
This is part of the reason why Sky has continued to invest in satellite technology, with Last saying that it delivers an effective broadcast regardless of the demand - something not guaranteed online, particularly with slower internet connections.
Spark has already released a statement saying it's mindful "some people may still not have adequate coverage to stream the matches at home" and that the company is looking at a range of options to ensure the content reaches a broad audience.
Spark has still not announced what those measures might involve, but the pressure will be on to ensure it delivers effective options for what will be the New Zealand's first predominantly digital Rugby World Cup.
What the deal means for fans
How will Kiwis be able to access RWC2019?
New Zealanders will be able to stream the matches over their broadband or mobile connection, via an app that will be compatible with a wide range of devices – including TVs, laptops, tablets and mobile phones. TVNZ will offer selected matches free-to-air.
How much will it cost?
Spark won't be releasing pricing details until next calendar year but intends to offer pricing options to suit people's differing preferences and budgets. This will include a full tournament package and individual match passes.
Which games will be screened free-to-air via TVNZ?
These details will be released in due course, but we can confirm there will be seven live matches screened free-to-air, and this will include the tournament's opening match and the final.
Will I have to be a Spark customer to watch the RWC2019?
No. We will be streaming the tournament over an app that will be available to all New Zealanders, no matter who their broadband or mobile provider is. The app will be compatible with a wide range of devices. It will be free to download and then matches and packages will be offered on a pay to watch basis. Selected matches will be also be available free-to-air via TVNZ.
What sort of free content might you offer online via the app?
Those details will be released next year, but the content is likely to include – for example – highlights from the week's play or delayed full match content.
What about people who don't have good broadband coverage – particularly people in rural areas?
The vast majority of New Zealanders can and do already access streaming services very effectively and that number continues to grow with UFB and RBI programmes roll-outs continuing. However, we are very mindful that in late 2019, some people may still not have adequate coverage to stream the matches at home. We want to do our best to give as many New Zealanders as possible to watch - so we are looking at a range of options. We're not able to give any details right now.
Source: Spark, TVNZ
