Yes it is attainable. But why would a digital piano help? Still the same notes
But as long as the note is still an A it shouldn't be much of an difference
I had a friend who tried to get perfect pitch and improved a bit, he used a chromatic tuner which produced notes. He carried this around with him all the time. Then he realized that he could use the chromatic tuner instead of perfect pitch...
It's hearing pitch 'colour'. If the colour is not in 440, then I guess you will be slightly confused because you don't know the colours, but you can still hear them.