Well, Heisenburg uncertainty becomes more relevant the colder you get. In this case, [uncertainty in position] * [uncertainty in momentum] >= ħ/2, so something with mass but no kinetic energy would be everywhere in an infinite universe with equal probability.
Ah, this definitely makes sense, so it's at the least not observable.
Another thing crossing my mind is whether Heisenberg uncertainity becomes relevant for these kind of experiments. I think we're talking about ~10^-7 K, thus ~10^-30 J mean energy. For a hydrogen atom (1 u), that would be roughly p = ~10^28 Ns. Hence, uncertainity of location would be h/p ~= 10^-6 m, i.e. in micrometer range, which seems quite large. Does this make sense?
Edit: It's aluminium in the experiment (27 u), but the numbers should be in the same ballpark.
Sounds about right to me. Wikipedia's list of Orders of magnitude (temperature)* shows atomic waves being coherent over centimetres at 10^-15 K, and a 10^8 difference in temperature is a 10^4 difference in momentum — which fits μm to cm.
