I was already assigning a bulk group id to all the items. I accomplished this with the following:
1. If item has bulk group id
2. If item is being inserted, not updated
3. Do a select into from a selection of items based on the bulk group id
Trigger
IF(@BulkGroupInsertId IS NULL OR EXISTS (SELECT * FROM DELETED))
BEGIN
-- Do Single Insert
END
ELSE
BEGIN
-- Bulk Insert
INSERT INTO TeamSubscription (DivisionTeamId, PhoneNumber, DateCreated)
SELECT tc.TeamId, p.MobilePhone, GETDATE()
FROM
-- Commented Out
WHERE
-- Commented Out
GROUP BY
-- Commented Out
END