Here is a study done about growing plants, vegetables in asphalt...it was very well done....It's the fumes when asphalt is heated that cause serious problems.....From the study:

Kovach, a scientist at Ohio State University’s Ohio Agricultural Research and Development Center, has been growing fruits and vegetables on an abandoned parking lot to test the best methods on what seems like an inhospitable site. He’s also growing the same plants in gardens created from an adjacent lawn so he can compare the parking-lot methods to more conventional conditions. read more

I’ve noticed that the triple mix from the city is often one part dunno, one part could-be-leaf mould and one part whatever. I don’t think it’s so much that the soil is polluted but rather that it’s just completely lacking in nutrients. I don’t think that hunks of asphalt would poison soil but I could be wrong. There could also be something else in there.

Asphalt does contain a host of heavy hydrocarbons (how's that for some asphalt alliteration?) some of which are toxic. Most notably the family of polycyclic aromatic hydrocarbons or PAHs. These also occur in soot, diesel exhaust, and airborne deposition from coal burning in decades past. They are ubiquitous but no less toxic for that. A 3" thick layer is likely to contain a significant amount of these. I myself would think twice or three times before growing food there, even though I am not certain what the uptake rates are for PAHs into plants. At a minimum I would not plant root crops, to decrease the exposure to trace amounts of actual dirt sticking to the vegetables. That will certainly help.

Another:

I found some papers about the uptake of PAH's into plants, and they suggested that a) it's low, and b) most uptake occurs via surface contact of leaves or roots to soil. Avoiding the parts that have been in direct contact with the soil (or by covering the soil with sand) seemed a good solution.

This is a very strange problem. I’ve never encountered soil that crappy. It sounds like it was the scrapings from the end of a pile and the machine managed to scape up asphalt and stones along with whatever other junk was there. Asphalt in the soil would not be good because of its petrochemical nature and what ever else might have been on it (vehicles etc) before the soil pile was placed. Plants would definitely take up these kind of things.

If the soil was purchased by the City from an outside supplier, they got ripped off. If the soil was a City product and made from municipal compost (likely) someone isn’t doing a very good job. (City compost isn’t very good in my experience but still, asphalt!)

I would get a parks supervisor to come out and see for themselves.

I don’t know of any testing services but I’m sure there out there. U of Guelph might be a place to start.