Looks like this deal is back. Sign up as a new user for Contact Mobile and $200 credit is added to your Contact Electricity account (within 7 days they say).
T&C's say it is targeted and:
The Offer is not available to customers who have previously signed up to a special Contact Mobile offer in the last 6 months and is not available in conjunction with any other offer
Old Posts:
https://www.cheapies.nz/node/46655
https://www.cheapies.nz/node/45832
FYI: I did get the email, signed up and am awaiting credit. Sadly I missed out last time when it was $300.