What do the brackets signify? Insignificance? Why are they only on some signs?

Having just done a weekend road trip from the south to the north, and back, we had a chance to relive some Tasmanian roadside quirks.

We like the weird use of brackets around some place names on some road signs.

What do the brackets signify? Insignificance?

Yes, we could ask the Transport Department, but we were hoping our readers might have suggestions.

EDIT: The answer