Notice about the core book.
p. 54, Cold Control
p. 59, Magnetic Control
For these powers, there are no exception for the immobilization options for Huge Creatures, while other effects preventing actions (such as Snare, Grapple, Stun, Sound Control, Light Control) do not effect Huge targets.
(Sorry, just realized this does not apply to Plant Control - that refers back to Grapple mechanism).