There are some people on the 401 who do have transit alternatives.
People can carpool (I know people who carpool to share the cost of the 407).
People can travel at different times to take advantage of lower rates off peak.
People can make different decisions about where they live and work.
By your logic, congestion charges would not be effective because those people already had transit alternatives to get into core areas. Yet congestion charges reduce traffic despite no new transit infrastructure being offered.
I think you are simply incorrect in assuming that existing travel patterns are immutable unless we build billion dollar infrastructure that takes a decade to deliver. Organization before electronics before concrete.