That's a really good question and a hard one to answer.
Personally, I can only say what I know about the French and Belgian scenes.
"Foreign legion" guys like Kimmage and (Robert) Millar followed the typical model that the French themselves applied and stilll apply: they lived initially where their clubs were based, then sometimes followed colleagues'/friends' recommendations. Never outside France except in the case of team
diktats.
Ditto here in Belgium, really. Self-supporting and -sustaining networks, club cycling and in a few (fortunate) cases, taxation still dictate where folks live and train here.
So, in summary, no(t much) change there.
One of the key factors necessary to dopers is isolation. What Wiggins once described as a monkish lifestyle is in fact just that: cloistering oneself can help with concentration and hide one's current level from rivals, but more importantly, it can keep other sorts of activities nicely hidden.
Etna and Teide are perfect sites because they provide the ideal conditions for numbers-based testing and training at altitude, but they also offer the requisite isolation. Except when the
Guardian comes around, of course.
The continuing value of this aspect of isolation is perhaps debatable nowadays with the introduction of the bio-passport, whereabouts logging and out-of-competition testing, but the habits are long-established and of course the numbers must still be checked.
Thankfully there are no itinerant paparazzi operating in cycling, otherwise there would be a lot more mobility than we currently have!