Hey there. I had a look into this for you, and there is no functionality within Outlook to directly open an OST file. The only options here are:
1. Use a 3rd party utility to view the file.
2. Write a batch/vbscript to convert the file to PST and then open it in Outlook.
Option 1 is best if you don't want to mess about with extra files etc and only have a requirement to view the info. This will be the quickest method but will mean that you aren't using the Outlook client to view the file.
Option 2 is best if you absolutely need to use the Outlook client and need to use the data within ie for forwarding/replying etc. This will be the slower option however.
It will be possible to execute either of options from a single command line entry., so hopefully that will satisfy your requirements.
I can help you out with either of these options, so please get back to me if you think I can be of some use. Happy to answer any further questions.
Thanks for taking the time to read this.
Kind regards,
Dave Hunter