There are several smaller companies in the so called conversion business using structured ASICs.
google for 137K hits and more than enough players
AMI, ViaASIC, Flextronic, and also some surprises in the google list like Honeywell and epson I had long forgotten about. The active ones will show up at DAC every year.
For other comments, you could also peek into John Cooleys website, lots of ASIC, EDA vendor feedback there, some very -ve. When you get interested in a particular vendor, research them thouroughly.
Since you mentioned cpu porting, I saw on opencores that the OpenRISC
1200 had been ViaASIC ed so I had a look at that, they reduce it down to a single via mask. They give very little performance info for the conversion though but suggest that most of the expected speed of full std cell is obtained, maybe 20% left behind. This core like most opencores was not planned for FPGA, dates back to the free ASIC IP hubris. A design planned for BlockRam FPGA should port very well to these like minded ASICs if only the mask costs can be lowered.
Their kits are 300-500K $ range for HDL in, GDS out for 1 mask. There have been some poor reviews of this SW, its perhaps still early days.
Not sure how they handle production and quantities, they claim 10x reduction in FPGA costs which shouldn't be too dificult if you have the volume.
One thing that seems obvious is project sharing, if ten projects share
1 mask over a full large die, you could probably get 10-20 designs out of. This is something that maybe the Mosis types should switch too rather than trying to share all masks per group. But if the 10x reduction is spread over 10 projects, back to square one.
What I found interesting was their macro block, something like a 1/4 BlockRam of 128 by 32 DP with around 256 logic cells each includes a FF and handful of gates. I can see right away I would need 2-4 of these for my cpu and that gives me some useful ASIC info to compare against FPGA or other full mask flows, long before I spend any time on ASIC design.
When CA wakes up, somebody from Xilinx will step up to the plate and trash every other vendor.
John