No, there's absolutely nothing in the frame to secure the housings.
I ended up running them short enough so they would bend well above the spindle. On this particular frame there's so much room above the spindle in the BB area that it works quite well. I did not bother with foam dampener. But I should have. It does rattle in the down tube and I can hear it rub when I turn the bars to their extreme left and right. Over time, that might not be too good for the frame. But I'm sure it never rubs in normal riding scenarios. Anyway, once I rebuild this bike on the replacement frame, I will probably address all these issues.
Ok, while I wait for the new cable housing's to show up, this is the idea I had in mind
Looking at the drive side of the frame, ie rear to your left, fork to your right
1. Rear brake cable housing & foam cover will go through top tube & I will have to enlarge the exit hole
2. Rear derailleur & front derailleur cables now go through down tube & under spindle, near the bottom hatch area
3. FD loops up into seat post to exit & RD continues through rear chain stay
The bottom hatch has a metal cylinder piece attached to it that would hold a Di2 battery or part
1. Simply tie a very thin zip tie at the base of the cylinder where it meets the plastic
2. Before pulling it tight, add 2 small zip tie loops on either size & clip & keep the circumference small for a housing to pass through
3. Add a drop of superglue to zip tie around metal so it wont move
This should allow you to have a foam covering on each housing in the down tube up until the BB starts & then the housing goes on its on
OR
Use a simple cable clamp around the cylinder with a bolt/nut & that makes the base wide enough that it retains the cables in place without needing zip ties or superglue
https://www.amazon.com/TICONN-42PCS-Cable-Clamps-Set/dp/B094YKZBKP/ref=sr_1_13?keywords=metal+cable+retainer&qid=1670342718&sprefix=cable+retainer+meta%2Caps%2C146&sr=8-13Edit:
After much thought (and 3 more cups of coffee), I realized that any simple rubber O-ring over the metal cylinder pushed to bottom will securely hold the cables on either side as the lower part of the attachment has a plastic base on which the cylinder is sitting
Edit #2
After another cup of coffee & a file I managed to do this as a test fit.
In practice the 3/4" plastic bushing will be reversed & it is a very tight fit & should hold the cable housings in place