HIPAA - Violation? Something does not seem right!

The company I work for has a sick leave police of unverified by a dr. or verified. My sick leaves in question were verified. The company is questioning this and has placed me on administrative leave, with pay. Lucky me! There are others in my same work category where the company has done this. Our union says sit back and enjoy the time off, this is the normal process. I was warned by the union that further sick calls dealing with the same issue will result in further company actions against me.
When the contract dr. used by the company is asked exactly what information is needed for proof that I am well or the other employee's we are told to provide all information.
When pressed as to the exact information that is needed we are met with strong resistance by the dr. and the company.
We are told to fill out forms that allow that company to get our medical information; however we are not told exactly what we are to provide. Our union official's merely warn us to be careful what information we provide in case the company finds other questionable issues.

If the company is not being specific as to the medical information they need and are hoping we provide too much medical information that may bring a verification of termination in some other area unrelated and the goal of the company is to set off a ripple effect throughout our group to be very careful in using sick leave or you may be place on administrative leave.
Is a corporation allowed to use these bully tactics with our medical information, especially when they will not inform the employee group of the exact information they need, such as dates and time frames that are in question.

Best Regards! And Thank You!

Nope no HIPAA violations at all. HIPAA prohibits your medical provider from revealing information about your diagnosis and treatment to anyone without your permission. There is nothing that prevents your employer from requiring to give that permission.

Everything you describe is strictly within the areas of company policy and union contracts.
If you weren't in a union, you could be terminated just for being out sick more than your employer likes. And they can demand to know everything about your condition.

'Our union official's merely warn us to be careful what information we provide in case the company finds other questionable issues.' Medical information is generally provided by your doctor(s), and what you fill out on a form is not expected to be detailed or given much weight, so sure, you don't say much. But you do have to allow your doctor(s) to provide information. The company can be denied insurance for example, if other employees or company clients are harmed in any way by your actions, and something like prescribed painkillers were kept secret. And you could be denied a comp claim. A company has a right to know if you could be a hazard at work.