Today I realized one thing: 427 - 409 serve as the effective collector lanes for 401 between 427N and Martin Grove.
Ps: 401W is completely closed Fromm Hurontario to Mavis in Sauga.
Once the collector lanes in Mississauga are done, the only place missing them will be 905 East (up to Oshawa). With the railway right to the south, though, we might be looking at a (2+2)+(2+2) configuration...