Masking at a pro lab is a requisite for using Ilfochrome Classic; there is very rarely a tranny, especially that can get away without masking.Unfortunately the mask also interferes with sharpness.
The printers are (were) Master Accredited (here in Australia). The problem with Ilfo' is the limited wiggle-room with contrast in the two media types. Images can lose from 2 to 3.5 stops through the process; I nailed a lot on Velvia, but a lot more were "at the margin" needing extensive masking and testing, and neither of the two media versions were ever 100% satisfactory. So, pro labs can afford to do it, but the cost will ultiimately be absorbed by the customer, which is why it was so very expensive. It was never "seamless" in terms of detail or tonal transitiions, but rather abrubt and jarring; there was room for a lot of improvement of the media, and why it never was improved has puzzled users for a long time.
4x5 sheet film comes up absolutely beautifully in the hybrid sphere — it really does, just beautifully; I love it, but I will not move on to 4x5 because I am concerned by Fuji's potential plans to trim off yet more lines form the reversal film stable, possibly later this year.