Of course its possible to land a job in IT from overseas without a valid visa to come over and actually work.
It's equally possible to land a job in any skilled occupation without a valid visa to come over and actually work.
Now I'm not saying it would be an easy task due to the amount of IT jobs and the high percentage of competition for those jobs.
Happens regularly or prospective migrants wouldn't ever be able to apply for a Temporary Work Visa or a Work To Residency visa.
As an applicant of these visas, you must secure a job offer to secure these visas.
Also, a lot of migrants need a skilled job offer from an NZ employer in order to achieve enough points on the EOI for a Residency visa via the Skilled Migrant Category to guarantee EOI selection from the pool at the next fortnightly EOI pull.....the job offer allows 50 or 60 bonus points.....and at this point of securing the job offer, an applicant wouldn't have a valid visa or even have submitted EOI.
What is illegal is actually working in any job in NZ without a valid visa unless of course you are a NZ citizen, and Australian citizen (with approved reciprocal rights) or Australian PRV holder (with approved reciprocal rights).