A little out of my league here and very confused. Was the "French 75" not in fact "Gun, 75mm, M1917", rather than the M1916? The M1917 was US-built copy of the British QF 18 pounder but rechambered for French 75 mm ammunition. During the early days of WW2 most, if not all of the US's remaining stock was sent to the UK where it was used for home defence and training. A number of these guns (18) reached Greece in January 1941. If any more were sent with the British Expeditionary Force, I do not know.
In the 2nd New Zealand Divisional Artillery's on-line history at:
Reference to this gun is made in a report by Brigadier Miles to General Freyberg which informed that "Many more anti-tank guns were needed, particularly heavy ones, and he suggested that French 75s fitted with Martin Parry adaptors and Beach platforms might be used." (Lessons of Greece, pg. 170)
This indicates to me, that the “French 75s” used in Greece were indeed horse-drawn types.