Nice graphic there. I'm a stickler for details so I recorded all the exact dates
Lakeshore West line
To Hamilton Center;
-total length(revenue service); 40.3 miles
-subdivisions; USRC 1.2, Oakville 36.1, Hamilton 3.0
-ownership; 32.2 GO(80%), 5.1 CN, 3.0 CP
(further increase in ownership difficult/unlikely)
-purchases;
2000 - USRC limits mile 0.0 to 1.2
2010 March 31 - Oakville sub mile 1.2 to 8.4 = 7.2 miles for $72 million
2012 March 27 - Oakville sub mile 8.4 to 23.6 = 15.1 miles(+14.2 miles of the Bala sub), 29.3 miles for $310.5 million
2013 March 22 - Oakviile sub mile 23.6 to 32.2 = 8.6 miles for $52.5 million
To James St;
-total length(revenue service); 40.5 miles
-subdivisions; USRC 1.2, Oakville 39.3
-ownership; 32.2 GO(80%), 8.3 CN
Niagara(seasonal only)
-total length(revenue service); 82.4 miles
-subdivisions; USRC 1.2, Oakville 38.1, Grimsby 43.1
-ownership; 32.2 GO(39%), 50.2 CN
Speculation - Grimsby sub is a lower priority line for CN it may be available for purchase at some point in the future.
Lakeshore East line(figures do not include trackage to Pickering south, 1.0 miles owned by CN)
-total length(revenue service); 31.5 miles
-subdivisions; USRC 1.4, Kingston 18.4, GO 11.7
-ownership; 31.5 GO
(100%)
-purchases;
2000 - USRC limits mile 332.4 to 333.8(center of Union) = 1.4 miles
2011 March 30 - Kingston sub mile 314.0 to 332.4 = 18.4 miles for $299 million
Milton line
-total length(revenue service); 31.3 miles
-subdivisions; USRC 1.5, Galt 30.0
-ownership; 4.85 GO(16%), 26.45 CP
(further increase in ownership difficult/unlikely)
-purchases;
2000 - USRC limits mile 0.0 to 1.45 = 1.45 miles
pre 2005 - Galt sub mile 1.45 to 4.8 = 3.35 miles
Kitchener line
-total length(revenue service); 62.7 miles
-subdivisions; USRC 1.6, Weston 15.4, Halton 13.0, Guelph 32.7
-ownership; 49.7 GO(79%), 13.0 CN
(further increase in ownership difficult/unlikely)
-purchases;
2000 - USRC mile 0.0 to 1.6 = 1.6 miles
2009 April 8 - Weston sub mile 1.6 to 17.0 = 15.4 miles for $160 million
2014 Sept 24 - Guelph sub mile 30 to mile 62.7 = 32.7 miles for $76 million
Barrie line
-total length(revenue service); 63.0 miles
-subdivisions; USRC 1.6, Weston 1.4, Newmarket 60.0
-ownership; 63.0 GO
(100%)
-purchases;
1998 Dec 1 - Newmarket sub mile 41.5 to 63.0 = 21.5 miles(City of Barrie purchase from CN)
2001 - Newmarket sub mile 15.5 to 63.0 = 47.5 miles(ownership transfer to GO from the city of Barrie & additional track purchases from CN)
2009 Dec 15 - Newmarket sub mile 3.0 to 15.5 = 12.5 miles for 68$ million
Richmond Hill line
-total length(revenue service to Gormley); 26.0 miles
-subdivisions; USRC 1.9, Bala 24.1
-ownership; 16.1 GO(62%), 9.9 CN
(further increase in ownership difficult/unlikely)
-purchases;
2012 March 27 - Bala mile 1.9 to 16.1 = 14.2 miles(+15.2 miles of the Oakville sub), 29.3 miles for $310.5 million
Stouffville line
-total length(revenue service); 30.7 miles
-subdivisions; USRC 1.4, Kingston 6.8, Uxbridge 22.3, 105(yard) track 0.2
-ownership; 30.7 GO
(100%)
-purchases;
1993 - Uxbridge mile 28.4 to 38.7(GO does not operate on the main track past mile 38.7, the only current user is York-Durhan heritage railway)
2001 - Uxbridge mile 38.7 to 61.0 = 22.3 miles
Total System length(figures do not include duplicate miles for different lines);
year round revenue service - 288.0 miles
with seasonal Niagara service - 331.1 miles
Total known cost of corridor purchases; $1,038 million for 116.9 miles
Ownership as of 1998;
213.4 miles = 11.7 GO(5.4%), 167.4 CN(78.4%), 34.3 CP(16.1%)
Ownership of revenue service mileage after extensions to Gormley & James St.
288.0 miles = 228.05 GO(79.2%), 30.5 CN(10.6%), 29.45 CP(10.2%)
including Niagara;
331.1 miles = 228.05 GO(68.9%), 73.6 CN(22.2%), 29.45 CP(8.9%)
Breakdown of line extensions since Dec 2007; 114.4 miles
-to Barrie Dec 2007 21.3 miles(GO)
-to Lincolnville Jan 2008; 2.1 miles(GO)
-to Niagara Jun 2009; 45.1 miles(CN)
-to Kitchener Dec 2011; 32.7 miles(GO) 0.6 (CN)
-to Allandale Jan 2012; 3.5 miles(GO)
-to West Harbour July 2015; 4.7 miles(CN)
-to Gormley work in progress; 5.0 miles(CN)
Addition corridor purchase, currently unused;
2010 CP Belleville sub (Don Branch) mile 209.4 to 206.4 = 3.0 miles
2014 CP Canpa sub mile 0.0 to 2.6 = 2.6 miles (rumored but unverified/unlikely)
To note GO's first corridor purchase was way in 1993! when they bought a portion of the Uxbridge sub from CN to prevent its abandonment.
But likewise, the only one I have never been able to exactly pinpoint is the Galt sub purchase. Imo I believe it happened at the same time as GO's purchases of the USRC but I can't confirm that. What I can confirm is that it occurred before 2004 as ownership of the section is shown as being GO's on the original RAC map I use to update ownership;
For those interested here's my updated 2015 version;