How to mount Safeboot encrypted Windows partiton in Ubuntu

You can't.

It's encrpyted. You didn't encrypt it so that your adversary could mount it in Ubuntu. On the contrary, you encrypted it so that none can mount it.

It may be telling you that /dev/sda1 is ntfs, maybe that's what's still written to the MBR but your encryption software doesn't care about the MBR table. If you could boot from another HD with Windows installed, it wouldn't mount this partition either.

What is written there is not a valid ntfs filesystem. It's something that only SafeBoot can understand after you give it your password.

Whether SafeBoot provides linux drivers that can read data from /dev/sda1 and make it available as a transparent ntfs filesystem, I don't know. I googled a bit and didn't find it.

PS: If SafeBoot indeed doesn't provide support to mount it under Ubuntu, which I believe is the case, perhaps you could try VirtualMachine solutions.