That nice Mr Google doesn't seem to find any relevant references with a search for "transient road", so the term doesn't seem to be in common usage.
"Properties rarely come on sale" seems to me to be just estate agents' hype, similar to terms like "once in a lifetime opportunity", "this offer can't last for long", "buy now to avoid disappointment", etc, which are found in adverts for all sorts of things. It's effectively trying to say "You'll regret not buying this house, as it's unlikely that you'll find another great opportunity like it anytime soon".
Such a term is probably more likely to be used for a 4- or 5-bedroom detached property in a leafy suburb (where many people live in their homes until well into their retirement) than for a 1- or 2-bedroom semi in a street largely populated by younger people (who might be looking to move when their job changes or when their family gets bigger).
So I'd tend to associate 'rarely comes on sale' as often associated with 'upmarket' properties and the term 'transient' as more likely to be associated with the lower end of the market.
However, from the point of view of a potential purchaser who might only be expecting to remain in one place for a fairly short while, 'transient' is a good thing as it means that it's likely that there'll be no shortage of interest when he/she wants to sell later on.