I was not aware that sandboxed users could see apps other users couldn't, as mentioned in the one of the answer - something for me to try!
The only other option I am aware of is to "side load" the bar file, you can side load with various tools which you can find if you search, such as:
http://forums.crackberry.com/blackberry-10-os-f269/how-get-bb10-hardware-id-sideload-app-bar-file-into-blackberry-10-a-780773/
http://forums.crackberry.com/android-app-sideloading-f279/how-sideload-apps-bb10-device-easy-way-windows-825656/
I haven't tried out these tools, sorry.
I actually do it using the tools you get with the Android Command line toolset - available from BB web site here:
http://developer.blackberry.com/android/tools/
but this approach are not 'user friendly'. I use it because I have converted a few Android apps to run on BB10 and so got to know the tools.
I can't say that these tools are safe, since I don't actually know them, but what I can say is that I am not aware of any way that a PC based tool sending something over the internet (or USB) to your BB10 could break it, nor am I aware of any way that a side loaded app could break your BB10. The days of bricking your BB devise with a dubious bit of software do seem (thankfully) to be over.
Edit: Just thought I would update this given the options that Nate has found, which I also didn't know about!
Both the sites Nate has found seem to work in the same way as the tools I mentioned above. My understanding of all these tools is that they run a deploy utility, that connects to the BB10 device via a TCP/IP connection (which could be routed over WiFi or USB), and sends the bar file over this connection. The connection is initiated by the deploy utility, which is why it has to be in the same network.
There is likely some BBRY proprietary protocol involved, which includes an exchange of the password, as the password supplied to the deploy utility must match the development password on the device.
Now I strongly suspect that BBRY have not published the specification for this communication. I also strongly suspect that the password is never seen in the clear, so you could not use some tool like Wireshark to reverse engineer this. My suspicions therefore is that the tools, including the two I have pointed you at, all run something like the Android Command line tool under the covers - and they got this from BBRY. So perhaps you can build something like the web sites yourself - assuming you have the time and inclination of course.
Just a thought and just my opinion.