Strong baseline. Two field notes worth adding from the LF Builders side, since interlock and flagstone work are core to what we do across the GTA.
On base depth - the 12-inch compacted granular base the guide hints at is the single most-skipped step in driveway and walkway interlock failures we see. Spring 2026 has been brutal for jobs installed at 4-6 inches of base because the contractor priced for that. We covered the failure mode in detail here for anyone weighing quotes: The 12-inch rule: why most Toronto interlock patios fail by spring. Same physics applies to driveways and the heave is worse because of the load.
On stormwater - for any Toronto driveway over roughly 30 sq m of new hard surface, expect Toronto Water to look at runoff calcs even on a residential resurface. Permeable interlock (PICP) qualifies, but the bedding course has to be 4-8 mm angular open-graded stone, not standard limestone screenings. If your contractor lists screenings on the spec sheet for a permeable system, that is a red flag.
Pricing in the guide is on point for early 2026. Edge restraint is where we see contractors cut - spec the metal or concrete edge, never plastic on driveways. The polymeric sand at the joints needs to be re-applied around year 5 to 7, factor that into long-term cost, not just the install price.