Yes it is, but UI updates must be done on the UI thread. This hold true for Winforms, WPF as well as the ArcMap/ArcCatalog windows.
This concept is mentioned in the link you provided: sections Updating the UI from a background thread and Calling ArcObjects from a thread other than the main thread should help. Basically, you create a Winforms Control on the UI thread, but do not display it anywhere and use it merely as a means to propagate calls to the UI thread. So any ivocations of IStatusBar.ShowProgressBar, IStatusBar.StepProgressBar etc. must be effectively done from the UI thread.
Of course, no matter what you do, you must always adhere to the fact that ArcObjects cannot be used across threads, as described in the article.
Another alternative might be to wrap your functionality in a geoprocessing tool and have it execute asynchronously by the ArcGIS framework for you.