Here's the thing.
If there's been a reactor in a herd, then it has been culled and the herd is on standstill until it every animal has had two clear tests. This is in case they are incubating the disease.
So even if it were legal to move the remaining herd to another spot, you risk taking the disease, currently incubating in its early stages and undetectable, to the new spot.
That's why it isn't legal.
It's really tough for your friends, but I am afraid there is nothing that can be done except wait out the standstill period and hope for two clear tests. If the landlord won't wait, then it's doubly hard but I am afraid equally unavoidable.