Depends on what you miss from BB - the physical keyboard? In that case then the Q devices would be for you.

If you miss the kick-ass email handling capabilities but like to have a big screen then any of the Z devices would do.

BB OS 10 did not support bis package..
so if you download movie using bb10, it will drain your data..

For what i read, sure cant support..even you subscribe the bis, it will eat your data like normal plan..no data compressing bla bla bla..

but maybe otai2 got trick..

You know, if you can really do that, I'm surprised. because if you can do that, that means you've just done something BIS was not invented for.

No. erm.. how should i Put it.
like this:
phone ---through BIS----> BlackBerry NOC -----internet-----> SERVER ----through internet--> BlackBerry NOC----through BIS----> phone
That's the picture I want you to understand.
Normal phones just connect to the internet. No BIS, no NOC. No security, no compression.
In your case, the video you downloaded should be charged under your data usage, BIS or not. However, that did not happened. For example:

100mb video that goes through BIS = 95mb in size (compressed, but only smaller)
100mb video that goes through normal internet = 100mb in size.
In your case, you claimed that your usage is 256mb per month. But after downloading a lot, you only used 5MB.
That's a lot of savings, and that wasn't what BIS was designed for.

That is why I'm surprised.

Is it an old BIS plan?

I get your point. I had lots of friends who just took the 25/month plan and use their Blackberry's for everything- communicate, stream, tether. Turns out even if over limit they just slow it down a bit. Perfect plan for students eh  and then they just buy small android phones for instagram etc using wifi.