I remember seeing this app a couple months ago and being excited about a team finally doing this. They've been available in New York City for a while and now they're trying to raise money to expand to more places. Hopefully they open source the app\server in the future since it would be great to have more co-op apps for the other "gig economy" style apps.
You might be able to say that drivers would be more likely to offer each additional resources (education or perhaps other more material resources) to ensure quality of service over investors who would be more likely to fire drivers. Others have pointed out that they have co-operatively owned taxi services in Europe and this doesn’t seem to cause issues in terms of quality control.
What I described seem to me to be the most evident biases and heuristics that the drivers would be subject to. What other biases and heuristics specifically are you concerned about?