(considering only the initial Series 1 lenses)
Vivitar was a 'commercial' brand, but they did not designed any lens. Either they specified what kind of lens they needed and had manufacturers design/produce them, or they directly used some already designed lenses (like the 'solid cat' mirror lenses).
As they sourced lenses from many manufacturers, mount conversion could be very different between Series 1 lenses if they are made by different manufacturers. Fortunately, the manufacturer is mentionned within the serial number of Vivitar lenses, so it is easy to check who built a lens.
Of course Tamron was not a company that Vivitar contracted, as the T4/TX interchangeable mounts was a lens range supposed to compete against Tamron's own interchangeable mount (which was then Adaptamatic).
Another consequence of the fact that they did not designed/manufactured lenses themselves is that in several cases you can find the same lenses as the Series 1 sold under different brands. Another consequence is that they sometimes sold the 'same' Vivitar lens but coming from different manufacturers (like the 70-210 zoom).