declare @half float = 0.0208333333357587;

((select count(1) from t where CAST([DateTime] as float) - CAST([DateTime] as int) >=      0  and CAST([DateTime] as float) - CAST([DateTime] as int) < @half)   as [00-30],
((select count(1) from t where CAST([DateTime] as float) - CAST([DateTime] as int) >=   @half and CAST([DateTime] as float) - CAST([DateTime] as int) < 2*@half) as [01-00],
((select count(1) from t where CAST([DateTime] as float) - CAST([DateTime] as int) >= 2*@half and CAST([DateTime] as float) - CAST([DateTime] as int) < 3*@half) as [01-30],
...
((select count(1) from t where CAST([DateTime] as float) - CAST([DateTime] as int) >=46*@half and CAST([DateTime] as float) - CAST([DateTime] as int) <47*@half) as [23-30]

DECLARE @tbl TABLE (d datetime, somedata varchar(10))
INSERT @tbl VALUES
('20170101 10:02:00', '1'),
('20170101 11:20:00', '2'),
('20170101 11:20:00', '3'),
('20170101 11:21:00', '4');

WITH Numbers(N) AS
(
   SELECT 1 UNION ALL SELECT N+1 FROM Numbers WHERE N < 48
), c AS
(   SELECT *, DATEADD(minute, @step * (N - 1), @s) t1, DATEADD(minute, @step * N, @s) t2 
   FROM Numbers 
)
SELECT   t1.t1, MAX(t1.t2) t2, count(d) n 
FROM c t1 LEFT JOIN @tbl t2 ON t2.d >= t1.t1 AND t2.d < t1.t2 
GROUP BY t1.t1