The Import Map option has been around since 0.55, but has received very little attention. It still technically works, but that isn't obvious. It needs some improvements, such as:
It would also be nice to add improved checking of resources matching up and so forth, but for now integrating with the map tab for BIQs both with and without previous maps is the primary goal.
I think this was done (except perhaps the resource-matching, although maybe that too?), but will have to check.
The first bullet point has been done at an indeterminate point in the past.
The second one... sort of.
- There is no warning about, "hey, there's already a map here, are you sure?"
- Showing the updated map works, but if and only if you are not on the map tab when you import it
There are also map rendering error warnings in some cases, likely due to resource/unit count mismatches.