That is really handy info! You saying those conversion tools can be used to convert Electrum priv keys? That would be easier then having your own Electrum full node server =) ... in the event Electrums server network goes down.
Yes. Assuming that by "Electrum priv keys" you mean the master private key that is generated by the "Mnemonic -> Seed -> xprv" conversion in Electrum. Once you have the "master" xprv, you can just put it into the BIP39 tool as described above and it will do most of the hard work for you...
AFAIK no-one has, as yet, created a standalone Electrum Mnemonic converter... but I've had a quick look at the existing BIP39 tool code and compared it with the Electrum source code... it seems like it would be a relatively trivial task to modify it to accept Electrum Mnemonics so you wouldn't even need to use the "getmasterprivate()" command to get the xprv... you could just put in your 12 word seed (and/or custom words) and away you go.
The only difference in "Mnemonic -> Seed -> xprv" conversion between Electrum and BIP39 is that Electrum uses a "default" passphrase of "electrum" instead of "mnemonic"... the other differences relate to the structure and checksum validation of the mnemonic, which would probably be just as trivial to implement, but aren't necessarily required if all you want is to convert the seed to addresses/keys.
NOTE: I actually did a quick dirty mod on the BIP39 tool code to test it... I just forced the mnemonic checksum validation to always return true, changed the default passphrase from "mnemonic" to "electrum" and voilà... it will take an Electrum seed, you set BIP32 and path as m/0 (or m/1 for change addresses) and it spits out the correct addresses/private keys
