Marvel has Netflix only series coming too, so its not a solid source. Their idea of connectivity is not the only one either. So far all we know for sure is that Arrow Flash and MAYBE Supergirl are connected. For most people the networks hardly matter unless you are trying to find the show. They watch the show for the show, not what channel its on.
Marvel being on Netflix is still within the Marvel universe per Marvel's design. But Marvel has also established its MCU brand as something that people are clearly interested in watching. So, at this point, any channel that aired a Marvel show would, presumably, be totally cool with airing an MCU show that ties in with other MCU material. Why? Because it's gonna make them money and they don't care about the competition.
Of course, Marvel probably wouldn't do that unless they got major bucks out of the licensing, simply because they already have an "in-house" television network in the form of ABC.
Warner Bros. has the CW and CBS, so it's possible the Supergirl show will end up connecting to the CW, but I still think that there might be competition between the networks. Ultimately, it's that network competition that would, I think, make a network reluctant to air a show that dovetails into another network's shows. All that does is send people to go watch the other network.
Netflix is a different animal. It's not competing with ABC. I mean, yes, it competes in the sense of "competes for viewer attention," but it doesn't compete for advertiser revenue in the sense of "Who's going to buy our ad time?" That's different from if, for example, Marvel aired an MCU show on NBC. NBC and ABC directly compete against each other both for viewers and for ad revenues.
DC, though, has had a "Batman" show on Fox, a "Vertigo" show on NBC (Constantine...which died a relatively quick death...), and the two CW programs. Oh, and I think I heard about another CW spinoff with Atom, Firestorm, and maybe Black Canary. Now it has Supergirl. I'd hope they tie it into the CW universe, but it's anyone's guess. And then there's the separate film universe. It's just nowhere near as unified as the Marvel brand.
The brilliance of Marvel's MCU and everything connecting is that it allows for MASSIVE cross-platform marketing, all with a unified brand. At this point, if you buy an MCU product, you know what you're getting regardless of where you get it. MCU TV show? MCU video game? MCU film? You know what to expect. That makes the brand both hugely valuable and immensely successful (assuming you don't let quality tank). But with DC stuff, you have no idea what you're getting. It's a lot more like saying "Hey, did you love the Avengers? Then you're gonna LOVE the new Fantastic Four movie!!" Well, no, that statement doesn't follow because they aren't being made by the same people and the two products have nothing to do with each other whatsoever.
