Surely it still runs to, then continues the other side of Lougheed Highway. It must still run all the way up to Hastings St.
We lived one block north of the highway (was dirt past Bainbridge for a time back in the '40s). And about 3 blocks toward Simon Fraser Uni off Sperling Ave. Bainbridge think it was dead ended at the driveway to our house. It's all subdivided there now.
You're right, there was no development at Burnaby Lake. We'd walk through bush to skate on it in winter.