Hi,
You can override the email content in order to add extra recipients to the email depending the order content but it won't be a perfect solution.
Basically, when an order contains several products, you don't want to send an email to the other company to notify him for the full order ; you just want to provide specific data for the specific products of this company.
And that's one of the goals of HikaMarket multi-vendor.
By using a multi-vendor system, you can assign specific products to a specific vendor (even if you don't gave him an account or access to manage the products/orders in the front-end).
When a product will be bought, HikaMarket will create "sub-orders" for the "vendors" and will notify them by email.
You can also add some restrictions like only send an email when the order is "confirmed" (so they won't be notified if the order is just created).
Otherwise, it is also possible to create a custom plugin to send extra emails to the different companies ; if you have the knowledges I would recommend it to you.
You can also contact an external developer but the price of the custom development might be higher than HikaMarket.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.