Are uber drivers allowed to be Lyft Drivers or regular Taxi drivers? If so, you have a good argument that they are not employees. If not, they will be seen by the CRA as employees, regardless of anything else in place.
If they are not employees, drivers are obliged to collect GST from Uber for their services if they earn more than $30K. If Uber re-sells that service, they are also obliged to collect GST from the end user. They can claim an input tax credit on the contractor's GST to offset. This is normal business operation in Canada, and one of the main reasons the HST was so popular - it moved all the multiple people charging and remitting taxes to one spot - the end sale.
If Uber's contractors are determined to be employees, that's a major issue for them, because at that point they have a ton of CPP and EI to pay that they have not been doing.
Really, they don't have much of an argument here either way. There is no real reason they should be tax exempt.
