Verticillium is a fungus disease of plants which can exist in a dormant form in soil for many years (much longer than two years).
It doesn't spread by any other method except direct contamination. If you work with dirty tools or wearing muddy boots, you can transfer it just as effectively over a distance of 8 feet or 80 miles.
On the other hand, there is no sense in getting paranoia about every possible plant disease you read about on the web. You might consider the UK Royal Horticultural Society statistics for the disease: the two most common species affected were trees, Acers (213 reports) and Cotinus (113). At the other end of htethe scale, there were a total of six reports for solanum species, and just three for blackberries.
Provided you keep your garden reasonably "clean and tidy", the likelihood is that you will never have problems with verticillium at all.
The most important consideration on where to plant crops is to rotate them, so you don't grow the same species in the same place for year after year. Obviously you can't do that for blackberries, where the same plants will produce fruit for many years, but if you grow your solanum species in the same place every year you will increase the risk of disease - but not necessarily verticillium.