Yes, you can tell on close inspection, Laurie, but not without invading someone's personal space
No, if you know what you're looking for, you can tell with the fit, hang, quality material at a reasonable distance.
if the car's an issue it's simple - park round the corner or use a taxi. Not that many highly paid professionals in a big city drive to see clients at all.
This will work/is true of London. But in smaller, more car dependent cities people drive all the time and see each other's cars frequently; at all agency meetings, court, conferences. I'm in Dublin (as car dependent as it gets) and my company (which is admittedly quite status driven) introduced a car allowance simply because one of the director's cars was old and shabby and it didn't give the right impression.
Like I say, I don't like this argument so I'm not even sure why I'm labouring the point. What I'm saying is, yes there are certain trappings of middle class jobs, but I'm not inclined to feel too sorry for people because they are generally paid well enough to cover them.