The individual who originally sent me a news tip about TWC not supporting CableCARDs in the Series 3 TiVo forwarded to me the following followup email which essentially states what we know (TWC will install CableCARDs in the Series 3 TiVo). I just thought I would post this so that we could put the whole TWC Series 3 TiVo issue to bed.
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Forwarded Message From: “Cust.Ops”
Reply-To: “Cust.Ops”
Date: Mon, 21 Aug 2006 09:55:46 -0700
To: XXXXXXXX
Subject: Re: Re: FEEDBACK_Customer_Service
Hello XXXXX,Thank you for your inquiry. We do supply CableCARD’s with our cable system. However, they are not two way interactive. The CableCARD will only be able to transmit channels and not allow Interactive programming such as the On Screen Guide, On Demand, Sports Packages and Pay Per View.
If the On Screen guide is downloaded directly from TiVo, then Yes, the CableCARD will work with it. However, if anything goes wrong with your TiVo system, we will not be able to support it (troubleshoot).
If you have any further questions, please do not hesitate to contact us at the number listed below. Our telephone representatives are available 24 hours a day, 7 days a week. Have a nice day! Time Warner Cable (888)TW-CABLE

Not sure this puts the issue to bed. Time warner will install the cablecards. They did so earlier this week in my Tivo3. They will however not send most HD channels thus rendering your Tivo3 a very expensive low dev DVR. I just had a technician explain to me why (they do it to save bandwith).
I had to install a TWC dvr to actually receive all HD channels.
mvanier,
I think what you’ve encountered is SDV. Take a look at this post….
http://www.tivoblog.com/archives/2008/10/04/where-oh-where-is-my-sdv-switched-digital-video-dongle/
It’s frustrating how TWC customer service is clueless – however I suspect they are kept this way in order to encourage TWC’s proprietary influence because they want to sell you their full line of services and products. It wouldn’t be in TWC’s best interest to be helpful with those who choose Tivo dvr’s and technicians over their own. We currently have a Tivo Series 2 which I would like to upgrade to the awesome gigantic HD XL. One benefit we’ve had with this older model is that we can always bypass the Tivo by switching out the cable to go from our TWC box directly to the TV and use the 2-way services (On Demand, etc) whenever we want. With a new Tivo HD upgrades, the box will be replaced by cablecard(s) and we won’t have that option available anymore. Honestly, we’d only bother to do it on rare occasion, but it was nice to know we could. Also, with the new system in place we’ll limit our some of the channel choices as they switch to SDV (must be a cheaper output option for TWC since it saves on bandwidth- another change that may eventually cause problems). I’m confident Tivo will eventually meet the SDV issue with future upgrades, but I’m hoping it will be some sort of accessory or new cablecard instead of a whole new dvr upgrade again!) However, the limitations a Tivo upgrade will cause are likely offset due to the extra services we’ll get from hooking the new dvr into our home network wirelessly (Netflix, YouTube, Amazon…). It’s expensive to upgrade and expand so many components at once, so I hope we will find lots of continued support from Tivo to keep our stuff up-to-date, regardless of what TWC or any other cable provider decides to change.
Make sure you request an SDV tuning adapter when you call TWC about your cablecards.