Is it possible to combine Mensural and Modern Barlines in one score?

Hello everybody,

I'm actually transcribing a Monteverdi score (for choir and Continuo) in order to be able to transpose it when ready. Therefore I would like to duplicate the format of the Original (view photo below: original score): the choir is written in Mensural Notation (with bar lines between the staves and with notes expanding across the bar lines without ties), while the contionuo is notated in the modern style (where notes expanding over two bars are tied together).
At first I thought that this wouldn't be possible because you have to choose whether to use the old notation style or not. But then I encountered the situation shown in the second photo below: in the right hand of the continuo part the notes are tied together, while in the left hand staff they are not.
Curiously, that's only the case in this measure - in other measures they are written without ties in all staves. I'm confused... Is this perhaps a bug? Or is it possible after all to choose the notation (with or without ties) for each individual staff?

If you want to check or experiment with my score, I added it to this post. I am talking about measure 14-15 here.

Thanks in advance for your help! :-)