I just spoke with InterbankFX. . .they have confirmed this.
On a standard account in 100:1 leverage, every standard lot is $1000 for your margin requirement regardless of the currency pair.
On a mini account in 200:1 leverage, every mini lot is $50 for your margin requirement regardless of the currency pair.
That means for pairs based from the AUD, NZD and the CHF, you are going to be paying a higher than normal margin requirement, however for pairs based from the EUR and GBP, you are going to be paying less than the standard margin requirement.
If you think about it, using a mini account, you're almost getting 400:1 leverage over the GBP established pairs.
To reply to your question, D, I don't know of any other broker that does this.