Strange custom scheduler data structure; creative / efficient solution desired

--- Make a tally table
--- See http://www.sqlservercentral.com/articles/TSQL/62867/ for information about tally tables
SELECT TOP 96
	IDENTITY (int,1,1) AS N
INTO dbo.Tally
FROM
	master.dbo.syscolumns AS sc1 
	CROSS JOIN master.dbo.syscolumns AS sc2
 
SELECT * FROM dbo.Tally
 
 
--- Make some test schedules
create table Schedule (
	[Date] datetime
	, [Availability] char(96)
	, [Staff] int )
 
insert into Schedule values('2008-12-01','XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX',1)
insert into Schedule values('2008-12-02','XXXXXXXXXXXXXXXXXXXXXXXXXXXXXAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAXXXXXXXXXXXXXXXXXXXXXXXXX',1)
insert into Schedule values('2008-12-03','AAAAAAAAAAAAAAAAAXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXAAAAAAAAAAAAAAAAAAAAAAA',1)
 
insert into Schedule values('2008-12-03','XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX',2)
insert into Schedule values('2008-12-01','XXXXXXXXXXXXXXXXXXXXXXXXXXXXXAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAXXXXXXXXXXXXXXXXXXXXXXXXX',2)
insert into Schedule values('2008-12-02','AAAAAAAAAAAAAAAAAXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXAAAAAAAAAAAAAAAAAAAAAAA',2)
 
insert into Schedule values('2008-12-02','XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX',3)
insert into Schedule values('2008-12-03','XXXXXXXXXXXXXXXXXXXXXXXXXXXXXAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAXXXXXXXXXXXXXXXXXXXXXXXXX',3)
insert into Schedule values('2008-12-01','AAAAAAAAAAAAAAAAAXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXAAAAAAAAAAAAAAAAAAAAAAA',3)
 
select * from Schedule
 
 
--- Get listing of staff available intervals
SELECT 
	  s.Staff
	, DATEADD(mi, (N-1)*15, s.Date) AS Date
	, t.N
	, SUBSTRING(s.Availability,N,1)
FROM 
	  Schedule AS s
	  CROSS JOIN Tally AS t
WHERE
	  SUBSTRING(s.Availability,N,1) = 'A'
ORDER BY
	  Date ASC
	, s.Staff ASC
 
 
--- Get staff available anytime between two datetime values with interval detail
SELECT
	  s.Staff
	, DATEADD(mi, (N-1)*15, s.Date) AS Date
FROM
	  Schedule AS s
	  CROSS JOIN Tally AS t
WHERE
	  SUBSTRING(s.Availability,N,1) = 'A'
	  AND s.Date BETWEEN '2008-12-01 00:00:00' AND '2008-12-01 17:00:00'
ORDER BY
	  s.Staff ASC
 
--- Get staff available anytime between two datetime values
SELECT DISTINCT
	  s.Staff
FROM
	  Schedule AS s
	  CROSS JOIN Tally AS t
WHERE
	  SUBSTRING(s.Availability,N,1) = 'A'
	  AND s.Date BETWEEN '2008-12-01 00:00:00' AND '2008-12-01 17:00:00'
ORDER BY
	  s.Staff ASC
                                              

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