In Tennis Alternative's interview of the Polish team, the Poles say that they were forbidden by the ITF to play on Taraflex.
The French played against Spain in 2010 on Taraflex, but I haven't heard of any other tie played on that surface (the usual version of "carpet" in the last decade) since then.
Does anybody know if the ITF's Taraflex ban is for all countries now or only for countries who never use it, even in futures ?
"For all Ties in the World Group and Zonal Group I the court surface must be of a type used in a Grand Slam Tournament or in a minimum of three Tournaments in the Men’s Professional Tour held in the year previous to the Tie. "
Not sure if challengers count, there were four last year on carpet.
EDIT: just saw someone posted above the prizemoney limit, so that's why.
There's some DC subclause about the underlayers for carpet, maybe they breached that.
Taraflex is also still a certified ITF surface, but the only difference with Davis Cup is they have a speed limit. An especially quick version of Taraflex would breach that, but a normal one would be fine (perhaps the Poles wanted to use superfast?). For perspective, the DC limit is way faster than any current ATP event, even quicker than Bercy 2010.
The Croats got spanked 5 years back for breaking the court pace limit - I've got the friction measurements somewhere, was like a 90s indoors court :-)