Not directly. I believe MrSid is a proprietary format so unlikely to ever get an importer. I do frequently use them though, all you need is some free software from the company that owns MrSid, they are called LizardTech and the software is called GeoViewer. Once you install the free software you open up all the MrSids you need and then run the export map command, and create a tif file with full resolution which you can then import into TBC. The same process also works for jpeg2000 files which is the newer version of MrSid.
I attached an instruction sheet I made for my employees awhile back. The version numbers have changed but its the same process, and of course the TBC import is to simply drag and drop. The steps you're looking for are numbers 9 through 18.