Selecting Records In SQL Server From Joined Table Where Timestamp Occurs Between Begin/End Range
You spelled out your solution:


  "I wish to join to Table2 to retreive Table2.UserStatus and
  Table2.UserStatusSubgroup where Table1.EventTimestamp occurs between
  Table2.StatusBeginTimestamp and Table2.StatusEndTimestamp"


    SELECT T1.*, T2.UserStatus, T2.UserStatusSubgroup
    FROM @Table1 AS T1
        INNER JOIN -- or LEFT OUTER JOIN to retain the rows with null userid
        @Table2 AS T2
        ON T1.UserID = T2.UserID
    WHERE /*(T1.UserID IS NULL) OR -- to retain rows with null userid  */
          T1.EventTimestamp BETWEEN T2.StatusBeginTimestamp AND T2.StatusEndTimestamp