I think companies have a right to know how their phones are being used, but the content of text messages is a different issue. It really hints a bit of big brother. I actually tried a web search to find out if this was still current but couldn't, so all I can say is if you use a company phone, be careful. Most cell phone companies avoid talking about how long text records are kept, but one said 3-5 days maximum. That said, your phone is always a liability as, even if you delete text messages, they might still be recoverable.
In my searches I did find several disturbing things. First was an article at www.eHow.com. This is from 2009, so the article may be outdated, but what caught my eye was the ads following the article.