Norma,
If you conduct a search of the Trenton/De Lorenzo thread at
http://www.pizzamaking.com/forum/index.php/topic,7841.0.html using Maggio as the search term, you will get several hits. Based on those posts, it does indeed seem clear that De Lorenzo's at one time used the Maggio mozzarella cheese. That cheese was shredded and came in unmarked bags. It was later reported, at Reply 115 at
http://www.pizzamaking.com/forum/index.php/topic,7841.msg45024/topicseen.html#msg45024, that the Maggio cheese was replaced by another cheese because of inconsistency problems. The Sargento cheese was mentioned, and a couple of us speculated that the new cheese was Grande cheese. Looking back now, I am not sure that the replacement cheese was Grande cheese only because Grande does not ordinarily use unmarked shredded cheese bags.
As can be seen at
http://www.maggiocheese.com/ , Maggio cheese products still exist. They are sold at retail in a multi-state area that includes Pennsylvania and New Jersey (
http://www.maggiocheese.com/findus.html). However, as was previously reported in the Trenton thread, Maggio's was sold in 1998 to Crowley Foods. At the time, Maggio had been using a New Jersey company to make their cheese under contract, as was reported in the article at
http://articles.philly.com/1998-07-15/business/25736696_1_crowley-foods-cheese-anniversary. I would be surprised if Crowley Foods is still making and selling the original Mazzio mozzarella cheese product that De Lorenzo's used. One can see the shredded cheese that De Lorenzo's now uses in the photo at
http://www.delorenzostomatopies.com/images/dtp-shoot08-untouched/pages/100_3160_JPG.htm and, on a pizza, in the photo at
http://www.delorenzostomatopies.com/images/dtp-shoot08-untouched/pages/100_3163_JPG.htm.
It will also be noted that Maggio's has a foodservice division. However, if one looks at the products at
http://www.maggiocheese.com/foodservice_selections.html, it will be seen that the only bagged mozzarella cheese is Part Skim Shredded Mozz, in 5-lb bags. From what I recall, De Lorenzo's was said to be using a pre-shredded whole milk mozzarella cheese.
For your purposes in making tomato pies, there is no need to try to emulate the De Lorenzo's tomato pies. However, the De Lorenzo tomato pies might serve as a style to consider in your efforts to make your version, particularly with respect to the types of the pizza sauce and cheese emblematic of that style.
Peter