The Tower ATC didn't sound too bothered either??
It is not in the power of ATC to stop anyone on a de-icing issue. It is the captain of that aircraft own and only responsibility. He is in the aircraft and (should) know what he has to do.
I know of some (small) companies that sometimes try to delay de-icing for ecomomic reasons. (e.i. to avoid the costs) But that is not the case with IB and major carriers.