13F Insight
DOSSIER · 13F Holders · Q1 2026
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
—
13F value held
$2.0B
visible holders
Holders
132
filers reporting
Concentration
23.59%
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 23.6% of the visible book.

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
Beutel, Goodman & Co Ltd.
CIK 0001361974
$153M5.5M1.04%Q1 202605
Turtle Creek Asset Management Inc.
CIK 0001484148
$138M4.9M5.17%Q1 202606
BANK OF MONTREAL /CAN/
CIK 0000927971
$88M3.1M0.03%Q1 202607
FAIRFAX FINANCIAL HOLDINGS LTD/ CAN
CIK 0000915191
$69M2.5M3.57%Q1 202608
VANGUARD CAPITAL MANAGEMENT LLC
CIK 0002100119· Index
$67M2.4M0.00%Q1 202609
JANUS HENDERSON GROUP PLC
CIK 0001274173
$65M2.3M0.03%Q1 202610
FMR LLC
CIK 0000315066
$64M2.3M0.00%Q1 202611
Connor, Clark & Lunn Investment Management Ltd.
CIK 0001596800
$64M2.3M0.15%Q1 202612
ACK Asset Management LLC
CIK 0001510940
$52M1.8M6.50%Q1 202613
FIL Ltd
CIK 0000318989
$50M1.8M0.04%Q1 202614
TD Waterhouse Canada Inc.
CIK 0001999606
$47M1.6M0.14%Q1 202615
Hill City Capital, LP
CIK 0001837343
$47M1.6M1.66%Q1 202616
TD ASSET MANAGEMENT INC
CIK 0001056053
$40M1.4M0.03%Q1 202617
Vinva Investment Management Ltd
CIK 0001968109
$37M2.1M0.45%Q1 202618
VAN LANSCHOT KEMPEN INVESTMENT MANAGEMENT N.V.
CIK 0001367401
$34M863K0.30%Q1 202619
Scheer, Rowlett & Associates Investment Management Ltd.
CIK 0001426327
$33M1.2M2.40%Q1 202620
Clearbridge Investments, LLC
CIK 0001348883
$31M1.1M0.03%Q1 2026
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