Hi rupphacker,
Yep, I believe you can do this, assuming the real estate listing form still has a description editor with html mode.
To accomplish this:
1) Create your real estate listing in Auctiva...you only need to fill out the item details section, which is the title through the counter, and save.
2) Go to your saved listings folder, check the box next to this item, and click the "Get HTML" button.
3) Copy the html in the pop up window.
4) Open the eBay real estate listing form and fill out the listing completely, except for the description fied.
5) Click the "Click here to enter your own html" tab on the description editor and paste the copied html in the editor.
6) Be sure to preview this listing before posting.
I'm not 100% sure that this will work, but as long as you preview the listing before posting, there won't be any risk to trying.
You could also post this listing as normal using eBay's real estate listing form and then come back and revise the item, pasting the copied html from the saved listing via the same process.
I hope this helps=)
-Mike