In no particular order, here are a bunch of neat papers and links on feral dogs.
The ecology and behavior of feral dogs: A case
study from central Italy, Boitani (from the Serpell book The Domestic Dog)
From the same book as above, Variation in dog society: between resource dispersion and social flux ...you won't regret the book. I don't have an electronic copy of this.
POPULATION AND SOCIAL BIOLOGY OF FREE-RANGING DOGS, Daniels & Bekoff
The Green & Gipson handbook on feral dogs
ECOLOGY OF A FERAL DOG PACK ON A WILDLIFE REFUGE Nesbitt (from Michael Fox's book The Wild Canids)
Age-graded dominance hierarchies and social tolerance in packs of free-ranging dogs
Feral dogs of the Galapagos This talks a lot about variables to consider, such as the effects of climate and food supply on the phenotype, and on the social and hunting behavior of the dogs.
More on the Galapagos dogs, including their eradication with 1080 laced baits, as is done to Australian dingoes. It's worth noting that these are recently introduced dogs, being culled to protect unique native wildlife... As opposed to the ecosystem's apex predator being destroyed to protect livestock.
[not quite ferals but...] Spacing and social organization: Urban stray dogs revisited
Ferals in Puerto Rico
Ferals and strays in Concepcion, Chile
An overview from Encyclopedia of Animal Behavior
Ecology of Feral Dogs in Alabama, Scott & Causey
Favara dissertation on Feral and Stray Dog Population Management
Short overview of feral dog management, though Extension
Dominance in relation to age, sex, and competitive contexts in a group of free-ranging domestic dogs, Cafazzo
Population ecology of free-ranging urban dogs in West Bengal, India, Pal
Factors influencing intergroup agonistic behaviour in free-ranging domestic dogs, Pal
Packs in Texas with links to other studies, including packing up to kill wildlife.
Input from Dr. Mark Johnson of GWR, probably the most experienced handler of feral dogs worldwide
Italy's feral dogs, article from the NY Times
Video, "Mountains damaged by feral dog packs"
Bison herd attacked by feral dogs
Rez dogs - catching stray and feral dogs on the Navajo reservation.
Some takeaways are that dogs are impressively adaptable and flexible animals. Whether or not they 'pack up' depends on things like their food supply and environmental pressures. Owned dogs, and dogs living directly off human support, may or may not form cohesive packs. They aren't required to for hunting, but often do simply because of the highly social nature of dogs. (A few people every year in the US are killed by packs of owned dogs, especially in the Southwest and/or on reservations. Ferals, though, are usually too afraid to approach a human.) Like coyotes and dingoes, ferals can and do pack up to hunt larger game. Multigenerational ferals tend to develop better social skills and cooperative groups. However, pup mortality is still very high, as they are less hardy than wild canids and domestication also took a degenerative toll on their parenting skills. Packs in rural areas can have quite a range, sometimes comparable to that of wild wolves.