Is it possible to use Back To My Mac DNS or routing information from the command line?
This has changed a little with 10.7 and you'll want to note that this uses IPv6 almost entirely so test with ping6 and traceroute6 to debug things.

It's no longer done via @computername.mobilemename.members.mac.com, it's now done via members.btmm.icloud.com, and its no longer as simple as your mobilemename.

Step 1: Find out your iCloud BTMM domain

Either of these commands will provide your BTMM domain:

# dns-sd -E
# mDNS -E


The output is formatted slightly differently, but what you're after is the numeric ID, it'll be something like 12345678.members.btmm.icloud.com.

Step 2: List Computers

You can use these tools to browse that domain for services, e.g. for ssh servers:

# dns-sd -B _ssh 12345678.members.btmm.icloud.com


Or if you already know the hostname just access it directly as computer-name.12345678.members.btmm.icloud.com. (Any spaces in your computer name will be hyphens in this domain).

You can only access this from a computer that is also set up for BTMM on the same account, because this hostname will resolve to an IPv6 address that is really the end of an encrypted network tunnel between your BTMM computers.

If you want to see the IPv6 address for a specific host, you can type

# dns-sd -G v6 computer-name.12345678.members.btmm.icloud.com


And it'll output something like:

17:37:47.504  Add     2  0 computer-name.12345678.members.btmm.icloud.com. FD11:993E:64AE:4DEA:011F:FBD1:F444:11A1%&lt;0&gt;  152


Step 3: Connect

# ssh username@computer-name.12345678.members.btmm.icloud.com


Note

I'm not sure if that number will ever change, so you may or may not need to repeat Step 1 at some point later on...