Is it true that ONLY American and Australian railroads have a
rail-spread of 4'8 1/2"?

Hi jingo,

Here is what I have found:

The Standard Gauge (4'8 1/2 or 41435 mm) is used in quite a few
countries, including Australia and the US.

The following page contains a list of railway gauges and where they
are used worldwide:
Railroad Gauge Width
http://parovoz.com/spravka/gauges-e.html

What makes "Standard Gauge" standard?
" While 4' 8½" (143.51 cm) is called 'Standard' in the United States,
Canada, the United Kingdom, Mexico, Norway, Sweden, and much of
continental Europe, other parts of the world consider their gauge to
be standard. "
http://www.microsoft.com/games/trainsimulator/articles_stdgauge.asp

Here is a brief history of the Standard Gauge in Britain and the US:
Wikipedia
http://en.wikipedia.org/wiki/Standard_gauge

And finally, an article in South Australia's 'Adelaide Review' on the
rocky history of Standard Gauge in Australia:
http://www.adelaidereview.com.au/archives/2004_04/issuesandopinion_story7.shtml

I hope this helps!

* j *

Metric correction:

The Standard Gauge is 4'8 1/2" or 1435mm.

Cheers.