Infinitely, sure, but within finite bounds, no, since muscle has lower energy content than fat, it is, in fact, possible to convert the latter to the former gaining mass without a calorie surplus.

OTOH, that’s not the real problem with CICO, the real problem with CICO isn't that it, or even simplified variations like “you can't gain organic mass on a calorie surplus” are wrong (though some of the latter are), or even that, in the relevant sense, calories out is hard to determine (and calories in may be too, if you count losses between mouth and digestion as reduction of “in” instead of increases in “out”), it’s that they aren’t, even if the quantities were certain, usefully actionable because they do not address the problems people in the real world have, which is why there are so many techniques aimed at observations regarding habit-building, satiety, etc., because the actual problem is compliance, not thermodynamic knowledge.