Don't know whether you could free them, Hazel, it'd be a pretty nasty snake by the time you did and they are one of the world's deadliest snakes. They are very fast too. Seeing they continue to hang around buildings if there is a food source, e.g. mice, you either need to get them relocated, or kill them. Sometimes they are found with their heads caught in soft drink cans, which they can't back out of , but those nets must also catch a lot. We had a live snake in a net, at ground level, when I had my dogs out in the same area for exercise one time.
Tammy spotted it just when I was going to take them back in and would not come away, I had to pick her up and carry her.
Thankfully no dog got bitten. That's not a big Brown by the way, I saw a 7 footer a mile from here, and Ian has seen 2 big ones like that down at the hay shed. You just know you are going to die if something like that bites you.