Experience everything Oblivion has to offer with previously released story expansions Shivering Isles, Knights of the Nine, and additional downloadable content included in The Elder Scrolls IV: Oblivion Remastered.

I’m pretty sure it’s at least being implied on the steam page that all the original DLC is included in the base game. And if you look at the deluxe upgrade:

Upgrade from the digital base game to The Elder Scrolls IV: Oblivion Remastered Deluxe Edition to receive:

• New quests for unique digital Akatosh and Mehrunes Dagon Armors, Weapons, and Horse Armor Sets
• Digital Artbook and Soundtrack App

It doesn’t look like it includes the “additional downloadable content” that includes the wizard’s tower.