This noise is only an inconvenience. The normal tube amp noise will drown it out when the master volume is high enough for rehearsal, shows, recording . . . .
I've cleaned all my sockets, ruled out tube issues (with a slight margin of error) and ruled out dirty power/lack of conditioner. a...
They do use laney amps live, and their live tone is great, especially Mike's lead tone.
When Steve Wilson's engineering the guitars, they use a variety of amps, but largely triple rectifiers.