Do you have 'privacy' for personal messages when using company phone or computer?

Imagine three scenarios:

1) You use your cell phone at work. 
You send a text message to your spouse. 
Your spouse sends a text message to you.

2) You are using your company cell phone at work.  
You send a text message to your spouse. 
Your spouse sends a text message to you.

3) You are using your company cell phone at home. 
You send a text message to your spouse. 
Your spouse sends a text message to you.

If you were never told of the company policy about cell phones, should you get in trouble for any of these?  Using your own phone at work, to make or receive a short text is not an issue.  And as long as you didn't use the company cell phone excessively, there probably wouldn't be an issue.  You send and receive a couple of text messages a day, no one cares.

Now, what if you were told the company policy.  And the policy states you cannot use the company cell phone for personal business.  Again, as long as you don't abuse the privilege, probably no one will care.

Now, you've been told the company policy stating you can use the cell phone for personal calls and text on your own time, but you need to pay for it.  Then there is no issue if you text during your off hours.  If you use it for personal calls and texts during business, you could, and should, get in trouble.

Lastly, you've been told you can use the company cell phone for personal calls and text during your off hours, but during your off hours, you send sexually explicit texts to your spouse.  Now what?  You are using it as instructed, you are paying to use it, should the company care what type of messages you are sending?

If you are using a company phone, don't expect to have everything you text as private.  It is there phone.  Even if you are paying for the texting you do during your off hours, it is their phone and the expectation should be that they will be monitoring communications.

Here is a news item before the ruling:  Justices hear case of Ontario police officer who sent risque messages (LA Times)

And here is a news item on the ruling:  Supreme Court allows reasonable searches of private texts on work-issued devices (Jurist.org)