What type of locks does BEGIN TRANSACTION cause against a specific table that's being read from? In the following example, what kinds of locks are generated from the explicit transaction block that wraps the SELECT INTO query?

BEGIN TRANSACTION T1

SELECT Field1, Field2, Field3
INTO TableB
FROM TableA
WHERE Field3 &gt; Value1

COMMIT TRANSACTION T1


Notes: 

1) TableA has about 100 billion rows, but the filter causes the query to return only about 5 million rows. 

2) Field3 is a clustered index on TableA, and the generated query plan is doing a clustered index seek.

3) The isolation level in my scenario is the default (READ COMMITTED).

Do explicit transaction blocks like this potentially cause more locking (or a higher chance of lock escalation) against the table then if the query wasn't wrapped in an explicit transaction?
5 million rows is a lot, theoretically it would cause shared lock escalation for TableA to table-level lock in any case (explicit or implicit transaction)

But you can find this out experimentally, you just need to setup Extended Events session and monitor for "lock_escalation" event

Then run your query in explicit and implicit transaction and check out XE session logs to see the lock_escalation events