A co worker, didnt believe me when I said there was no block heater for the 8.
He called a local dealer, (not the one I bought from) and asked if there was a block heater.
They said yes. He asked if they were sure. He was told the managers 8 had an rx7 block heater put in his car.
I called my dealer and asked about the block heater and was told no.
I told him about the other dealer. He said to call him back in 15.
I did. Here is what I was told.
They installed a mazda rx7 block heater in the frost plug. Even though I read in these forums that there is no frost plugs, I was told there was.
My dealer said the other dealer wouldnt not tell them wether or not Mazda Canada approved this procedure. I cant see the other dealer doing this if it werent approved.
My dealer is going to look into this and see if Maz can will give it their blessing.
I will report back as I get the info.
Maybe we finally have a block heater solution?
Temro (block heater company) is located in Winnipeg. I will see if the Mazda dealer even approached them for a solution yet.

Can I ask which dealers?

Gerry Gordon Mazda on Pembina supposedly has the heater installed in the demo RX8 the manager is driving.
I bought my car from Gautier Mazda, and since they owe me a block heater I would like them to do it rather than pay Gorden's.

Update:

Dealer confirmed a working rx7 block heater in an rx8.
It works and can be done.
However Mazda Canada has not given it their blessing and should the installation cause any problems no warranty.
They are currently working on an authorized solution for the rx8 blah blah blah.
So not an option in my opinion.
I will install some synthetic oil, and a battery blanket/and/or trickle charger and away we go.