I don't have an exact answer to your question, but I don't believe property tax assessments have taken place in any part of Philadelphia for 20 - 30 years. Philadelphia's current property tax system works through changing millage rates (by increasing or leaving them unchanged). I'm not sure if you've been following the news about the BRT lately (Board of Revision of Taxes), but that was the group responsible for keeping up with property taxes in the city and they have been doing a poor job.
There is currently a hold (moratorium) on all property tax assessments in Philadelphia for the next 2 years while the city rebuilds this division. If you have any questions about taxes on different properties in Roxborough, please let me know how I can help. I live in Green Tree Run in Roxborough and work for a local, start-up real estate company called Brown McKinney http://(www.brownmckinney.com).
Check this article out to learn more about the BRT & Assessments: