What part of Windows Phone do you think is well suited for a tablet?
The kernel is shared, and the developer APIs are quite similar and probably will be nearly identical in a future version. You can today write a C++/DirectX Game, that basically runs on both Windows 8/RT and Windows Phone.
The UI certainly is similar, I think horizontal tiles are better for a tablet than vertical.
The inter-app-communication with search and share and contracts is a lot better on Windows 8 than WP (WP multitasking is horrible).
I think hardware support, battery life, connected-standby are all very similar.
Plus it totally makes sense to leverage all the System-Center/Intune/Group-Policies stuff for managing tablets in an enterprise.
Windows 8 has VPN, Miracast, multiple Apps on the screen and very nicely designed bing apps. And in the future, there will be windows store Office apps…