The white shuttle buses say Impark and also DLC Transportation, which I think is its subsidiary.
http://www2.impark.com/pages/default.aspx?lang=en&region=philadelphia

Of the many sightings I can choose from in recent memory, the one that stands out would be the DLC Transportation Services vans that I pass every single morning parked along 15th street (between Walnut and Sansom Sts). There are usually at least two parked and they sit there idling, often times doors wide open and the driver standing outside. As I pointed out, there are usually a few of them and I'd guess that I see them every day before 9AM.

via idlefreephilly@cleanair.org

Thanks for writing! Clean Air Council will be writing a letter to this company, as well as adding this location to our regular database of idling hotspots. Please make sure to report this if you see it again!

FYI, when I passed the same spot today, 4/15, at 8 a.m., 2 DLC vans were parked and idling, a driver was standing outside one van's open door, and a 3rd van was pulling up, ready to sit and idle. This was at 15th street (between Walnut and Sansom Sts).

Thanks for writing! Clean Air Council will be writing a letter to this company, as well as adding this location to our regular database of idling hotspots. Please make sure to report this if you see it again!

FYI, when I walked along 15th St. today, May 12, three white vans from DLC were again sitting there, idling away. I have not ever seen them with their engines off in that location since I opened this complaint. I'm glad to know the Clean Air Council is writing the company. But somehow I doubt these drivers will care.

I wonder if the businesses that they are idling in front of (including a coffee shop with outdoor seating) could aid in the effort to ask these drivers to turn off their engines.