Yes, it is possible to get thru' on some cool tracks but not obvious. Took me a couple of failed attempts to do just that to work it out, as the tracks weren't mapped (and the entrances are hidden)....And then Strava came along.
https://labs.strava.com/heatmap/#15.24/151.26167/-...
Andy & I ran from Berowra to Manly once via Terry Hills and then Oxford Falls. We were going to swim across the river at the bottom of the Sphinx stairs at Bobbin Head, but a canoe turned up at exactly the right time. If you do it on Saturdays you can factor in a sausage from Bunnings on the way thru.