SQL SERVER PIVOT table with joins and dynamic columns

Since you want to transform data from rows into columns, then you will want to use the PIVOT function. If you have a limited number or known values, then you can hard-code the query:

select plan_id, [2012, November], [2012, December], [2013, January], [2013, February]
from
(
    SELECT 
        b.plan_id, 
        (Convert(varchar(4),b.run_year) + ', ' +  DateName(month,CAST('1900-' + Convert(varchar(2),b.run_month) + '-01' AS DATETIME))) AS billdate, 
        ISNULL(b.total_premium,0) + ISNULL(a.total_adj,0) AS total
    FROM cteBills b
    LEFT JOIN cteBillsAdj a 
        ON a.run_month = b.run_month 
        AND b.run_year = a.run_year 
        AND b.plan_id = a.plan_id
) d
pivot
(
    sum(total)
    for billdate in ([2012, November], [2012, December], [2013, January], [2013, February])
) piv;

But if you have an unknown number of values, then you will need to implement dynamic SQL:

DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX)

select @cols = STUFF((SELECT  ',' + QUOTENAME(Convert(varchar(4),b.run_year) + ', ' +  DateName(month,CAST('1900-' + Convert(varchar(2),b.run_month) + '-01' AS DATETIME))) ) 
                    from cteBills
                    group by b.run_year, b.run_month
                    order by b.run_year, b.run_month
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT plan_id, ' + @cols + ' 
            from 
             (
                SELECT 
                    b.plan_id, 
                    (Convert(varchar(4),b.run_year) + '', '' +  DateName(month,CAST(''1900-'' + Convert(varchar(2),b.run_month) + ''-01'' AS DATETIME))) AS billdate, 
                    ISNULL(b.total_premium,0) + ISNULL(a.total_adj,0) AS total
                FROM cteBills b
                LEFT JOIN cteBillsAdj a 
                    ON a.run_month = b.run_month 
                    AND b.run_year = a.run_year 
                    AND b.plan_id = a.plan_id
            ) x
            pivot 
            (
                sum(total)
                for billdate in (' + @cols + ')
            ) p '

execute sp_executesql @query;