13F Insight
DOSSIER · 13F Holders · Q1 2026Most-boughtAI cap-ex
ATS

ATS CORPORATION

132 institutions still hold ATS CORPORATION as of Q1 2026. Tracked across SEC 13F-HR filings, with insider and 13D/G activity surfaced alongside.

CUSIP 00217Y104·132 13F holders·last filed Mar 31, 2026
Market cap
—
▼ 0.6%
vs prior quarter
13F value held
$1.8B
52.0% inst. owned
of float
Holders
132
+48 QoQ
filers reporting
Activity
+87 / −34
+894 added · −868 reduced
this quarter
Concentration
25.16%
MASON CAPITAL MANAGEMENT LLC #1
top holder share
AI Holders Summary · Q1 2026

132 institutions reported ATS in Q1 2026. MASON CAPITAL MANAGEMENT LLC leads at 25.2% of the visible book. +48 net new institutions vs prior quarter — accumulation reading.

Top holders

Sorted by position value. Source: SEC EDGAR 13F-HR filings.

#HolderValueShares% port.Quarter
01
MASON CAPITAL MANAGEMENT LLC
CIK 0001218735
$463M16.4M75.48%Q1 202602
ROYAL BANK OF CANADA
CIK 0001000275
$219M7.8M0.04%Q1 202603
EdgePoint Investment Group Inc.
CIK 0001481669
$202M7.2M1.62%Q1 202604
Turtle Creek Asset Management Inc.
CIK 0001484148
$138M4.9M5.17%Q1 202605
BANK OF MONTREAL /CAN/
CIK 0000927971
$88M3.1M0.03%Q1 202606
FAIRFAX FINANCIAL HOLDINGS LTD/ CAN
CIK 0000915191
$69M2.5M3.57%Q1 202607
VANGUARD CAPITAL MANAGEMENT LLC
CIK 0002100119· Index
$67M2.4M0.00%Q1 202608
JANUS HENDERSON GROUP PLC
CIK 0001274173
$65M2.3M0.03%Q1 202609
FMR LLC
CIK 0000315066
$64M2.3M0.00%Q1 202610
Connor, Clark & Lunn Investment Management Ltd.
CIK 0001596800
$64M2.3M0.15%Q1 202611
ACK Asset Management LLC
CIK 0001510940
$52M1.8M6.50%Q1 202612
FIL Ltd
CIK 0000318989
$50M1.8M0.04%Q1 202613
TD Waterhouse Canada Inc.
CIK 0001999606
$47M1.6M0.14%Q1 202614
Hill City Capital, LP
CIK 0001837343
$47M1.6M1.66%Q1 202615
TD ASSET MANAGEMENT INC
CIK 0001056053
$40M1.4M0.03%Q1 202616
Vinva Investment Management Ltd
CIK 0001968109
$37M2.1M0.45%Q1 202617
VAN LANSCHOT KEMPEN INVESTMENT MANAGEMENT N.V.
CIK 0001367401
$34M863K0.30%Q1 202618
Scheer, Rowlett & Associates Investment Management Ltd.
CIK 0001426327
$33M1.2M2.40%Q1 202619
Clearbridge Investments, LLC
CIK 0001348883
$31M1.1M0.03%Q1 202620
Marathon Asset Management Ltd
CIK 0001861026
$31M1.1M1.18%Q1 2026
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