Most of us are familiar with the desert storage for mothballed airplanes (big one near Tuscon). Any chance airlines will retrieve equipment from there to replace the grounded 737 MAX planes?

My guess would be no, due to several reasons:

The "MAX" has been out just for a relatively short time, and while a few hundred airplanes seem to be a lot, there always exists some kind of reserve (recently taken out of service aircrafts that are still at a normal airport, wetlease) and even cancelling a few flights here and there would be cheaper than reactivating any desert bird.

Plus, most aircrafts brought there were shortly before next heavy maintenance, thus it would take quite some money and time to bring them back into service.

Unless the grounding would be for an extended period of time (ie, over 3 months - entirely possible) I can't see this happening.

Agree -- depends on grounding period. For legacy airlines like AA, it likely just means extending the retirement date of planes like the MD88.

For newer airlines like Norweigian it'll prove to be a bigger challenge -- fleet is too young to have planes even eligible for retirement. More likely it means they have to cancel routes that the 737Max8 was capable of performing (like short TATL) or upgauge to the much bigger 787 on those short, thin TATL routes -- either option will be very costly for the airlines and you can be sure they'll be looking for compensation from Boeing (either in the form of $$$ which a cash-strapped company like Norweigian likely needs or favorable discounts on future airline purchases / conversions of 737 Max to other Boeing planes)

For most airlines (at least in the Northern Hemisphere), we're still in low season so they will generally have less full schedules and less full planes. They'll simply allow the slack to be taken up with existing resources.

It's more likely airlines will wet lease aircraft and recoup (or at least try to) the cost from Boeing.

More likely this and the bigger airlines will be successful in getting costs recouped from Boeing. Airlines like Norwegian will struggle to get money from Boeing barring a class action lawsuit. I can see Boeing offering compensation to Chinese airlines, Emirates (flydubai), AA, WN, etc. But they will not bend over for smallish airlines at all, unless they are forced too.

It all depends on how Boeing handles this.
If Boeing offers official compensation to any airline, all other MAX users have easy way paved to get their compensation as well.
If Boeing offers something under the table to big players and says it's not compensating anything to anyone, it might be harder.

I don't see Norwegian as a small airline (fleet of ~150). Take into account the fact that they seem to have some financial issues, they might not care about good relations with manufacturer and sue them quickly if not compensated.

Even smaller airlines like Enter Air in Poland (fleet of 22, including 2 MAX; and 4 MAX on order) told the shareholders that it will recoup MAX costs from Boeing.

Will recoup the costs?
How can they be so sure?
The reason for the statement would be to avoid a panic-selling of their stock.

Boeing is turning PR handstands to avoid admitting fault for legal / liability reasons, while at the same time heavily revising the Max's software and training regime, so they're really on a tightrope here. Offering to reimburse stricken airlines for Max-related costs might be read as acceptance of blame. Boeing will put on a concerned and mournful face in the public square but play hardball in private. In the Lion Air case, because the Max in question exhibited control trouble the day before the accident, Boeing will argue fiercely that Lion Air was negligent in dispatching the plane on the fatal flight. With customers stuck with grounded Max fleets, Boeing is apt to argue: go take it up with your national aviation regulators. We didn't issue your ground order.

Anyway the Max is likely to be sidelined for only a couple of months -- not as long as it would take to de-pickle desert airplanes and get them online. How long it will take to coax the flying public back aboard the "now even safer" Max is anyone's guess.