In going through early editions of Canadian Railway & Marine World I found
a monthly column about freight car distribution, which may be of some help
in discussing the question. I didn't print every column off from the
microfilm, but I did print two out for now, from March 1922 and April
1930.

The March 1922 column says:

"Freight Car Locations on February 1.
"The Railway Association of Canada has issued a statement showing the
location of freight cars on Feb 1, based on reports received from the
following railways: Algoma Central & Hudson Bay; Canadian National,
including Grand Trunk Pacific; Canadian Pacific; Central Vermont in
Canada; Dominion Atlantic; Edmonton, Dunvegan & British Columbia; Grand
Trunk; Kettle Valley; Michigan Central in Canada; Napierville Jct.; Pere
Marquette in Canada; Quebec Central; Quebec, Montreal & Southern;
Temiskaming & Northern Ontario; Temiscouata; Toronto, Hamilton & Buffalo;
Wabash in Canada. The following are the figures: Cars owned by reporting
railways, 223,008; home cars on Canadian lines, 13,715; home cars on US
lines, 35,418; home cars on home roads, 173,875. Canadian owned foreign
cars on home lines, 12,173, US owned cars on foreign or home lines,
17,623, total cars on lines, 203,671; percent of cars on line to total
owned, 91.3; deficiency on line to total owned, 19.337; home cars in bad
order, 18,602; foreign cars in bad order, 446; total cars in bad order,
19048; percentage in bad order, 9.3; privately owned US cars on line,
1,682; privately owned Canadian cars on line, 1,013."

The April 1930 column says:

"The Railway Association of Canada reports location of freight cars on
March 1, based on returns from Algoma Central & Hudson Bay, Canadian
National, Canadian Pacific, Dominion Atlantic, Kettle Valley, Northern
Alberta, Quebec Central, Temiskaming & Northern Ontario, Temiscouata, and
Toronto, Hamilton & Buffalo Rys., as follows: cars owned, 204,306; home
Cars on Canadian lines, 9,128; home cars on USA foreign lines, 20,424;
home cars on home roads, 175,754; Canadian owned foreign cars on home
roads, 6,406; US owned foreign cars on home roads, 20,802; total cars on
lines, 201,962; percent on lines to total owned, 98.8; deficiency on line
to total owned, 2,344; home cars in bad order, 12,051; foreign cars in bad
order, 158; total cars in bad order, 12,209; percent in bad order to cars
on line, 6; privately owned USA cars on line, 3,164; privately owned
Canadian cars on line, 1,079."

The first thing that strikes me as interesting is that there were more US
foreign cars on a given home road than there were foreign Canadian cars,
and the percentage of home road cars on home roads is much higher than
I've seen mentioned for US roads.

A quick analysis of the 1930 data gives this:

US cars in Canada, 10.3%
Canadian cars in US, 10.1%
Home cars on home roads, 86.5%
Home cars on Canadian foreign roads, 4.5%

Is there available anywhere such data from American roads to compare with?

And lastly, a short but amusing news piece from the March 1921 issue of
Canadian Railway & Marine World:

"In speaking at a recent Canadian Club dinner in New York, Hon. N.W.
Rowell, MP for Durham, Ont., said: "E. W. Beatty is the only young man of
prominence Lord Shaughnessy has produced. Our guest may not be so proud of
it, but when Trotsky lived in New York he also worked for the C.P.R.
here." Lord Shaughnessy added, "True, and we still owe him $40.""

Frank Valoczy
Vancouver, BC