Well... I'd say, "have you tried it?" As written, no, that won't work. But that's because you haven't told PowerShell to actually execute your Get-Content. In double quotes, that's normally done as a subexpression, a la "blah blah $(Get-Content whatever.txt)". If I were experimenting, that's what I'd try first.
Thanks for the reply Don, I didn't really mean to ask will this work, it's more whats best? I mean i could just create loads of DSC Group Resources in the script and assign the Name, Description and members, but that doesn't seem like the best way to do it.
I could populate the hash table with individual groups, but then the hash table would be massive, so i suppose i have answered my own question and should use get-content or import-csv, unless there is a better way?