No, it wouldn't be cal/mag after the neutralization occurs.
If your pH down is phosphoric acid and it reacts with dolomitic limestone it will create
a mixture of calcium phosphate and magnesium phosphate. Carbon dioxide is released
as gas during this reaction.
I believe ca/mag is comprised of both calcium nitrate and magnesium nitrate which
are both a lot more soluble than calcium phosphate and magnesium phosphate.
So the answer is still no it would not be cal/mag that you create.