At the very least it happens in Flanders. I've seen ijs ("ice") capitalized in cursive as Ys[0] on an ice truck, for example.
Edit: from Wikipedia[1]: "It used to be common, in particular when writing in capitals, to write Y instead of IJ."
So it's an obsolete practice...
----
0. something along those lines: http://alphabetprintables.org/alphabet_printables_cursive/up...
There's even a section about this on wikipedia: https://en.m.wikipedia.org/wiki/IJ_(digraph) subsection "technical details".