the 2 isometry classes of irreducible [12,8,3]_2 codes are:

code no       1:
================
1 1 1 1 1 0 0 0 0 0 0 0
1 1 0 0 0 1 0 0 0 0 0 0
1 0 1 0 0 0 1 0 0 0 0 0
0 1 1 0 0 0 0 1 0 0 0 0
1 1 1 0 0 0 0 0 1 0 0 0
1 0 0 1 0 0 0 0 0 1 0 0
0 1 0 1 0 0 0 0 0 0 1 0
1 1 0 1 0 0 0 0 0 0 0 1
the automorphism group has order 48
and is strongly generated by the following 5 elements:
(
1 0 0 0 
0 1 0 0 
1 1 1 0 
1 1 0 1 
, 
1 0 0 0 
0 1 0 0 
1 1 0 1 
1 1 1 0 
, 
1 0 0 0 
0 1 0 0 
1 0 1 0 
1 0 0 1 
, 
1 0 0 0 
1 1 0 0 
0 0 1 0 
1 0 0 1 
, 
1 1 0 0 
0 1 0 0 
0 0 1 0 
0 1 0 1 
)
acting on the columns of the generator matrix as follows (in order):
(3, 9)(4, 12)(7, 8)(10, 11), 
(3, 12)(4, 9)(7, 11)(8, 10), 
(3, 7)(4, 10)(8, 9)(11, 12), 
(2, 6)(4, 10)(8, 9), 
(1, 6)(4, 11)(7, 9)
orbits: { 1, 6, 2 }, { 3, 9, 12, 7, 4, 8, 11, 10 }, { 5 }

code no       2:
================
1 1 1 1 1 0 0 0 0 0 0 0
1 1 0 0 0 1 0 0 0 0 0 0
1 0 1 0 0 0 1 0 0 0 0 0
0 1 1 0 0 0 0 1 0 0 0 0
1 0 0 1 0 0 0 0 1 0 0 0
0 1 0 1 0 0 0 0 0 1 0 0
1 0 1 1 0 0 0 0 0 0 1 0
0 1 1 1 0 0 0 0 0 0 0 1
the automorphism group has order 576
and is strongly generated by the following 8 elements:
(
1 0 0 0 
0 1 0 0 
0 0 1 0 
1 1 1 1 
, 
1 0 0 0 
0 1 0 0 
0 0 0 1 
0 0 1 0 
, 
1 0 0 0 
0 1 0 0 
1 1 1 1 
0 0 1 0 
, 
1 0 0 0 
1 0 0 1 
1 1 0 0 
0 0 1 0 
, 
1 0 0 0 
1 1 1 1 
1 0 0 1 
0 1 0 0 
, 
0 1 0 1 
1 0 0 1 
1 1 1 1 
0 0 0 1 
, 
0 0 0 1 
1 0 1 0 
0 1 0 1 
1 0 0 0 
, 
0 1 1 1 
0 0 1 0 
1 0 1 1 
1 0 0 0 
)
acting on the columns of the generator matrix as follows (in order):
(4, 5)(9, 12)(10, 11), 
(3, 4)(7, 9)(8, 10), 
(3, 4, 5)(7, 9, 12)(8, 10, 11), 
(2, 7, 9)(3, 4, 6)(8, 11, 10), 
(2, 4, 7, 5)(3, 12, 6, 9)(10, 11), 
(1, 10)(2, 9)(3, 5), 
(1, 4)(2, 7)(3, 10)(5, 8)(6, 11), 
(1, 4, 12)(2, 11, 3)(5, 9, 8)(6, 7, 10)
orbits: { 1, 10, 4, 12, 11, 8, 3, 7, 5, 2, 9, 6 }