A deal too good to be true?

Okay so I have an iphone 3g and I've had service on Rogers wireless for almost a year with it. My current plans are a talk time plan and their "value bundle" for iphones that includes 500mb/mo of data, unlimited texting/video messages and call id, visual voice mail.

I'm currently on the road for a few weeks visiting family in another town and while taking a break at a motel along the way I decided to call Rogers to see if there existed some kind of temporary plan to boost the amount of data usage allowed for this month because I'll be out at a camp away from internet access. I've been tethering my iphone to my laptop. The woman I talked to put me on hold for a few minutes then came back and told me she was able to put me on some kind of promotion going on right now where I get 3 months of unlimited data (which I assume to mean 5gb based on the fineprint to their other plans), but the weird thing is I didn't have to sign up for any new services or anything, nor will I have to call and cancel it at the end of the 3 months, apparently it will just automatically end.

What I'm basically wondering is if theres some kind of catch that she neglected to mention. It seems odd to just call and get unlimited data for 3 months without having to spend a penny or add any services. Does this kind of thing happen often?