I realize that these are tough times, even here in Canada, but that is absolutely no excuse to tie your 12 year old dog to the door of the SPCA, with a note saying that you can't look after it anymore. You took that pet on. For TWELVE YEARS. You have a responsibility to that pet. A duty. And don't be telling me that you are broke and can't feed it because I've seen homeless people with their dogs, trolling around town. I don't see them tying their dogs up to the doors of the SPCA.
If you love your pet there is ALWAYS a way around a tight situation. And I'm not talking public handouts.
Shame on you.