I am looking for the equivalent of the ATS fabric for Ontario (shapefile). The ATS fabric in Western Canada is quite easily found online, but I can't seem to find any good data for Eastern Canada, Ontario in particular. I'm willing to pay for the data, but does anyone know which vendors would have this data, instead of going to them and asking one at a time?
You may want to look at Teranet http://www.teranet.ca/ Teranet is the provincial organization responsible for property data. Let it be known that Teranet data is expensive.
Stumbled across this 2.5 years later. In Ontario, as the previous responder has said, the data is managed by teranet, which is a private enterprise (though owned by a public pension fund). In many cases individual counties, townships, and conservation authorities have purchased access for their GIS departments. In some cases, it is a layer available through their online mapping applications, example Frontenac County, and query-able as WMS or even as an ArcGis feature server. This may be helpful to you if your use case is fairly local, though unhelpful if you want a geographically broad solution.
That's the technical angle. You'll have to consider the nature of your use and licensing issues. I'm pretty sure if you use this for a public-facing application the lawyers will come knocking: the counties etc may make the data available, but I strongly suspect there are redistribution restrictions in the data licenses. Teranet's business model is the paid provision of this information, and it made significant investments digitizing it (and maintaining it since then) that some consider a Faustian bargain by the province, but this is not "free" public information.
In Québec, the data is publicly owned and distributed by the Ministry. Just like Ontario, many local governments also make it available through their geoportals.