I had a look at disklocker, but using bdemount seems a lot simpler. You don't need to decrypt anything just unlock and mount as NTFS.

Install

sudo add-apt-repository universe
sudo apt install libbde-utils

Check recovery identifier

This will show key protector types and recovery identifiers

sudo bdeinfo /dev/sdb3

Assuming bitlocker partition is 3 on secondary drive, aka sdb3, with your recovery key xxxxxx-xxxxxx-xxxxxx-xxxxxx-xxxxxx-xxxxxx-xxxxxx-xxxxxxx .

mkdir /tmp/a /tmp/b
sudo bdemount -r xxxxxx-xxxxxx-xxxxxx-xxxxxx-xxxxxx-xxxxxx-xxxxxx-xxxxxx /dev/sdb3 /tmp/a

This should expose a single raw file bde1 of the full size of partition, /tmp/a/bde1

Loop mount this raw file read only, giving /tmp/b as the partition contents, (contents of the ntfs filesystem)

sudo mount -o loop,ro /tmp/a/bde1 /tmp/b

Thus you should now have /tmp/b/Windows etc.

Or (on newer Ubuntu > 16)

sudo losetup -fP /tmp/a/bde1

then you can see it and mount and unmount in Nautilus as a user.