B0Real is an option of B0 (default False). If set to True, B0 is assumed to be real and the relation B0[a,0,a] = 2 + B0[0,a,a] is applied.
By default the arguments are not assumed real.
B0[s, 0, s]\text{B}_0(s,0,s)
With B0Real->True, transformation is done.
B0[s, 0, s, B0Real -> True, B0Unique -> True]\text{B}_0(0,s,s)+2