Will tires with spikes on a loaded heavy touring bicycle puncture the tubes?
The current generation of pre-manufactured winter tires you'd get from brands like Schwalbe do not use 'screw-in' style studs that have a point on the inside surface.  They have a pocket and flange design:



I don't know of a source for actual data on this other than personal anecdote, so I can offer that.

I have never had the stud on a commercially made/retail bought winter tire come through the casing and damage a tube, and I've never heard any of my colleagues complain about it.  But I have never used particularly cheap ones/off-brand, and most people around here have Marathons because that's what the stores here stock.

Certainly with a Marathon PLUS your studs are already outside what is supposed to be an industry leading protective layer, so I don't know what else you could do if it were a concern.

On the other side most of the so-called 'old timers' at the bike co-op will still recommend splitting and fitting an old tube on the inside of a winter tire if asked.  This bit of wisdom seems to be corroborated by Chris H's answer where some people have reported inconsistent quality with Schwalbes.  (Perhaps it is worth the extra $ for the 'Plus' model!)