Shares of handset designer BlackBerry (NYSE:BB) jumped as much as 10.5% overnight on about double the stock's normal trading volume. But most of the gains faded fast, and BlackBerry traded just 2.4% above Wednesday's closing price at 1:30 p.m. EDT.

The company reported fourth-quarter results this morning, and it was a mixed bag. Sales fell 36% year over year to $2.7 billion and missed Wall Street's $2.8 billion targets. But adjusted earnings of $0.22 per share were a welcome change from the expected $0.31 per-share loss.

The company's cost-savings program was completed one quarter ahead of schedule, leaving BlackBerry with lower operating costs and a more efficient business model. The so-called CORE program should reduce operating overhead by $1 billion annually going forward. Without this intiative, the company would have reported a significant loss this quarter.

BlackBerry also enjoyed $112 million in tax benefits this quarter. That's another line item that makes the difference between positive and negative earnings. So it's not like the long-awaited BlackBerry 10 launch saved the company's bacon single-handedly.

Is the Z10 handset saving BlackBerry's bacon or not? Nobody knows.

CEO Thorsten Heins hammered home the message that customers are excited about the new platform, and early sales are strong. Don't forget about that record-breaking million-unit order, folks! Also, the keyboard-equipped Q10 hasn't launched yet and should appeal to BlackBerry's core fans in a way that the touchscreen Z10 never will.

On the other hand, Heins avoided questions about expected and actual unit volumes like an Olympic-grade dodgeball champion. Here's a telling sample:

"There's a huge dynamic in the market, what is flowing in, what is already flowing out. So don't take it really kind of like a clear number, but what we see roughly is that from what we have shipped into the market, two-thirds to three-quarters already have sold through."

In other words, we should all get excited about BB10's lifesaving powers, but let's not get too specific about expectations. Also, Heins said he sees "strong marketing support" from American launch partner AT&T (NYSE:T), which doesn't seem to jibe with field reports on Z10-pushing in Ma Bell's stores.

So the raw numbers look promising, but management didn't inspire a whole lot of confidence in BlackBerry as a sustained turnaround story today. There's nothing in here to change my long-term view of the company and stock, which is a solid thumbs-down CAPScall