A good source to understand this topic is the journal article "Aspects of Italian Immigration to Philadelphia" by Joan Younger Dickinson. It was published in The Pennsylvania Magazine of History and Biography, Vol. 90, No. 4, October 1966, pp. 445-465.
You can purchase it from JSTOR at http://www.jstor.org/stable/20089965.
Can we find useful genealogical information in a journal article like this? Here are a few subjects covered in this article that I think would be helpful for those researching Italians from this city.
1. The names and opening years of the first Italian parishes in the city. Helpful to determine which parish your ancestor might have attended.
2. Where in the city and surrounding areas they congregated.
3. Immigration waves and provinces of origin.
4. Information on fraternal and other organizations whose goal it was to help Italians get established.
5. A frank discussion on the padroni system.
6. Information on living conditions.
7. Occupational percentages.
8. Citations pointing to other valuable sources of information.
These are but a few of the valuable subjects in this article and I encourage you to purchase and read it, even if your ancestors settled in a different part of the country. Some of the information is universally useful, such as that on the immigration waves.
