The headline that went with this article read "Landlord Limited Companies Could Cost Double".
As ever, the devil is in the detail and depends on the approach taken to investment. IF income is extracted from the company and IF there is a liability to NI Contributions by both the company and the owners then there is a potential for an effective tax rate of 50%.
Those are two pretty big IF's which is why they are in capitals.
As with any business the tax consequences of any decision can be profound and quality advice is required to make the most of the BTL opportunities.