The changes in behavior have been remarkably rapid--less than 60 years to effective domestication. Andrew Wagner warns that there may still be some residual issues.
"[You can be] sitting there drinking your cup of coffee and turning your head for a second, and then taking a swig and realizing, ‘Yeah, Boris came up here and peed in my coffee cup,’" said Amy Bassett, the Canid Conservation Center’s founder. "You can easily train and manage behavioral problems in dogs, but there are a lot of behaviors in foxes, regardless of if they’re Russian or U.S., that you will never be able to manage."
"Never" is a long time.
(*) That doesn't seem too crazy for an exotic. Some rare dog breeds are up there too: e.g. a saluki for $2500.