This entire thread fails to recognize a variety of factors that, to me, indicates Amtrak will never have a surge capacity/reserve fleet of their own.
First and foremost, money. WHERE would Amtrak get the money to buy 13 or more (as proposed above) full 'trainsets to be stored'? Once the new Acelas' come online, there may be a couple used in secondary corridor service, but that would undermine the pricing structure of the Acelas. (For what it's worth, I'm on an Acela as I write as the same trip on a regional train in business class was THREE dollars less! Thank you, Amsnag!) So in all likelihood, expect most to head to the scrapper. Note, too, they are 4" wider than all other 'standard' passenger equipment in North America, which limits their usefullness to SEPTA or other electrified commuter routes.
Maybe, when Amfleets start being replaced in MAYBE 5+ years, some will still be viable if they don't have cracked center sills, etc.
Part II of the money issue is where to store the 'fleet' when not in use. Amtrak has little trackage of their own and adding any at WAS or CHI, for example, would be beyond expensive. And don't forget the property taxes levied on properties with tracks...it ain't free folks!
Part III of the money issue is maintenance. I make no pretense at knowing or understanding the required inspections and frequencies, but it's likely any cars and locomotives coming from storage have to go through a FULL inspection & repair/replace gaskets, pumps, whatever as necessary.
Part IV of the money happens if Amtrak chooses to store equipment on some 3rd party property. Rent isn't free, either.
Part V of the money is 'return on investment'. Whether it's new cars, just-retired cars, or leased cars, if the wheels aren't turning the ROI is ZERO! No money manager, VP of accounting, or CEO would ever justify spending significant amounts of money 'just in case' or for 2 weeks per year. While holiday decorations fit the 2 weeks per year category, how much decorations has anyone seen other that at retail outlets? Corporate America pinches every penny these days. Corporate America is not 'Doomsday Preppers', or even 'overflow business preppers', either.
The second big issue is labor. Simply put, WHERE would Amtrak find a short-notice trained staff to actually PERFORM the inspections and repairs needed to get each car ready to roll? It's not like calling up 'We Work Today' and warm bodies descend on the property to do the work.
Don't forget the onboard staff, either. Cars need staffing. OBS people that have been furloughed, including dining car staff, likely have other jobs by now and can't just take a couple weeks unpaid leave to return to Amtrak. Again, Instant-Staff-R-Us is not an option. And don't forget T&E crews, either.
Another issue is sleeper furnishings such as blankets and pillows, and even food requirements that exceed 'normal' long-term contracted levels and rates. Can the food suppliers instantly increase their provisions by 20% for a couple days or a week?
As an example, take a look at the freight railroads that have stored many locomotives during downturns in business and laid off countless operating and maintenance staff as a result. Due to PSR they cut, cut, cut to the bone. If everything runs smoothly, their operating ratio got super low and the stockholders cheered. How many of those laid off employees are willing to come back in 2, or 5 years from now when business takes off again? What about a winter in Chicago like they had a couple years ago where there was a total breakdown of operations and it took months to recover?
With all the cuts that have occurred at Amtrak in the past 30 years, perhaps the biggest is the lack of funds to procure and replace equipment on a timely basis. Regardless of what's under construction today or RFPs in the works (Amfleet replacements), all that can be done is to simply 'replace' existing fleet levels with minimal expansion, if any. It would be fantastic if all rolling stock was replaced every 20-25 years and the displaced stock used for creating new trains, new routes, etc. But that won't happen any time soon, in my opinion.
Bottom line, ever since Amtrak came into being on May 1, 1971, it has been fight for survival. As long as Congress holds the purse strings, they'll never get ahead. Yes, when the Superliners were new, they created a couple of experimental routes like the Desert Wind and Pioneer. But as equipment became less and less availalble due to wreck damage, etc, those routes were among the cuts. The same holds true with North Coast Hiawatha and the National Limited. Lack of funding as well as funds for even more equipment doomed useful, but not sufficiently patronized routes to be eliminated. And due to various route segments being abandoned, most can never be restored.