I already have my four years bachelors evaluated by WES.
I have acquired a new 2 year bachelors (which is equal to diploma for ECA purposes). Is it okay if I use a different service (ICES) for this evaluation or do I have to stick to WES?
You don't have to stick with WES, you can use any service accepted by CIC. It makes no difference for CIC which service you use, as long as your credentials have a valid ECA.
I already have my four years bachelors evaluated by WES.
I have acquired a new 2 year bachelors (which is equal to diploma for ECA purposes). Is it okay if I use a different service (ICES) for this evaluation or do I have to stick to WES?
Yes you can use a different service. FYI, adding another credential to your WES ECA will be a cheaper option provided your university is recognized by WES.