Tunnels work but are "slowed down" to the point of 9600 baud in general (as soon as the traffic goes outside of China). The GCF *detects* encryption and either "kills it" or "slows it down to a snail's pace" (I have one other way around it but I am not going to publish that).
We had some of our employees move back to China (rural mainland, don't remember the details) and he had continued to use our tunneling VPN setup. We were using IPsec AH-only (not the most common ESP). This is a VPN technology that doesn't use encryption (Encapsulating Security Payload) but only authentication (Authentication Header). There wasn't any overt blocking or slowing down of our traffic, besides the usual problems one would encounter anywhere with the rural DSL provider.
IPSec AH is fully supported in Windows since XP, other OS-es supported it even earlier. It is also well supported by the very cheap Netgear Prosafe VPN/firewall devices, we've used FVS114 and FWAG114. Those are "business class" but have "home/residential" prices. Now they are officially obsoleted, don't know the replacements, but we still have them deployed and in use in many locations.
If you want to try it: do test this first on a LAN between two computers and then between same two computers over the same local ISP. Only after those tests are successful try intercontinental tunneling that could be really affected by the Chinese government censorship.
AFAIK there are no commercial providers for the AH-only service, you'll have to have your own tunnel exit somewhere in your homeland.
My information is couple of years old, Bitcoin did exist then, but probably wasn't an issue. Aside from the regular business use it was used (and it was helping unthrottle) with Bittorrent.
Edit: Also, please post some additional information regarding what you are observed as being blocked/throttled:
1) Bitcoin mainnet vs. Bitcoin testnet
2) incoming vs. outgoing connections to/from TCP port 8333/18333
3) does the non-coin-related TCP/IP traffic over the same ports flow properly?