Yes and yes.
To simply add the company name to both address entries change "/admin/new_customer.php" around line 354 from:
Code:
'entry_firstname' => $cInfo->billing_firstname,
'entry_lastname' => $cInfo->billing_lastname,
'entry_street_address' => $cInfo->billing_street_address,
to:
Code:
'entry_firstname' => $cInfo->billing_firstname,
'entry_lastname' => $cInfo->billing_lastname,
'entry_company' => $cInfo->entry_company,
'entry_street_address' => $cInfo->billing_street_address,
Adding a second field to add a different company name for the billing address is a little more work, but could be done as well.