Normally, a dialog opens using whatever is the "Current Working Directory", and there are a couple of ways to set this in Maya. However, notice how both of those "commands" start with a capital (uppercase) letter? this means they are not strictly real commands, but "RunTimeCommands", which are like aliases to commands or scripts that take no parameters.
This basically means a) there won't be any params you can add to these to control their behaviour, and b) because they are "shortcuts" to god-only-knows what code, there's no guarentee that setting any configuration (i.e. setting the "current working directory") beforehand will have any effect.
You do have a couple of options. First, just try setting the current working directory, then see what happens when you use those commands.
cmds.workspace(directory='d:/my_projects/props')
If that doesn't work, you need to query the underlying code of each of those runTimeCommands to follow what they are doing, and then replicate that yourself. This will probably involve the fileDialog2 command, which you can also set the starting folder with.
code = cmds.runTimeCommand('CreateReference', q=True, command=True)
apologies if the code is not 100% accurate, I'm not at Maya atm so am going from memory. This should help get you started a bit though.