Just to make sure you understand... the temporary tables still physically reside in tempdb. They still show up in tempdb.sys.tables and tempdb.sys.columns (indexes, constraints, etc.) They are just of the collation of the contained database instead of tempdb.

For instance, if you run this in a contained database:

USE ContainedDB;

GO

CREATE TABLE #TestTable (

RowID INT IDENTITY PRIMARY KEY CLUSTERED,

SSN char(9) NOT NULL UNIQUE,

Age tinyint CHECK(Age>18));

CREATE INDEX IX_TestTable ON #TestTable (Age, SSN);

declare @object_id int;

set @object_id = object_id('tempdb..#TestTable');

select * from tempdb.sys.tables where object_id = @object_id;

select * from tempdb.sys.key_constraints where parent_object_id = @object_id;

select * from tempdb.sys.check_constraints where parent_object_id = @object_id;

select * from tempdb.sys.indexes where object_id = @object_id;

select * from tempdb.sys.objects where type = 'U';

You will get returned to you all of the meta-data from tempdb for this temporary table.