Is the sample ramping applied to samples' current frequency or to mixing frequency?
That question doesn't make much sense. Ramping affects the sample's volume, and the ramp length is specified in samples, so the sample rate doesn't matter.
Ok, so it's f.e., ramp is 16 samples, and that's applied for samples' given frequency? I got the point, I think that samples were resampled to 48KHz and then apply the sample ramp. Damn silly question, duh.
The ramp is applied during mixing, so it does not depend on whether you play e.g. a sample at C-4 or C-5 - it will always have the same ramp length.