Hi Lynda,
I'd agree that it seems likely that he was in/around 3rd Ypres, although the Australian Divisions were not involved until well after "the big push" he mentions (they were fed in in September). Railway companies would be held at Army level, and thus would be used independently of any other Australian forces, which were held against I ANZAC (1,2,4,5 Divs - in GHQ reserve) and II ANZAC (3 Div, NZ Div & a British division - holding ground taken at Messines, to the south of Ypres, in June) at the time.
Can't give you an answer, but a possible location for one.
(Obviously, I don't know if you've checked this, so sorry if I'm teaching you to suck eggs)
Go to the National Archives of Australia's RecordSearch -
http://www.naa.gov.au/The_Collection/recordsearch.html
Search on Broad gauge railway company, All Words, Date Range 1910-1925. (note "broad gauge" - two separate words)
That gets 65 Hits. Click on Display and you will see their holdings. It includes:
5th (59th) Australian BGRO [Broad Gauge Railway Operating] Company: Brief record
War Diaries for:
3rd Section, Australian Railway Troops, and 59th Company (Australian), Railway Operating Division RE, and 59th Australian Broad Gauge Railway Operating Company - September - November 1917 (Diary covers September-November 1917 and has appendix containing history January-June 1917)
5 BGROC - Jan 1918, April-Dec (monthly) 1918, Jan, Feb, Mar, Apr-May 1919
59 BGROC - Dec 1917, Feb 1918
and Field Returns:
5 BGROC - Jan-Apr 1919
and a couple of Courts Martial
None of these
specifically cover the period you want, but the first two I mention have a good chance of containing info you are after.
I haven't examined the contents of any of these are they need to be ordered from NAA.
I must add that I am amazed that anyone still referred to "Taubes" as late as mid-1917. The Taube was long out of service by then, and though the name had been used generically by British and Commonwealth troops to include any German aircraft, I would have thought the term would have gone out of vogue before the end of 1916.
Just shows to go you...