thx1200 It isn't exactly the same as OWA. For starters, my shared inboxes do not show in OWA, but they show in the new Outlook. I would have to open another tab to see a shared inbox using OWA. Plus I can't add additional accounts in OWA, this is only available in the new Outlook. I would assume Microsoft would start citing these two reasons as to why Basic and E1 doesn't have access to the new Outlook for Windows.
Regarding it being available outside of business for free, that is because of the ad model, which people already complained about. It is free because of the ads that are injected into Outlook. I assume Microsoft came to the conclusion they would not be able to do that for businesses as they are already charging a license fee for basic and E1.
However, personally if Microsoft is charging you for email access to begin with, why not just allow access to the email client (new and old). I feel this would better position their product against alternatives, but for whatever reason they opted not to do so. Until they move on that, the new Outlook is just not available to basic and E1.