What options are there for Company A to access data from Company B network (same physical location). Best practises? Worst?

Hi All,

I'm looking for the best way to allow access to another company's server from within our network (We are both located on same physical site). At the moment Company B have limited infrastructure and the setup is below.

Current Setup

They have an application server that grabs some info from vehicles at one or two points.

Company A has a much larger network and we are looking to assist them them grabbing the necessary data and piping it through to their application server. Future setup will be something along the lines of this.

Future Setup

I'm fairly fresh into the networking space coming from a sysadmin role and would like to know if there are any recommended solutions for achieving this.

Some points below

According to Company B this application\server does not have the ability for us to just pipe their data through the cloud and grab it from there. We are a remote site, with each company having their own internet connectivity. This is not the fastest and we would prefer to not have to rely on WAN links and to keep this data local. Their IT Dept has asked us if it would be possible to open up a trunk port to our network. I know this can technically be done, and even secured in limiting certain vlan's \traffic etc etc.

I feel like although this is possible there is most likely better options available that would not be directly connecting our network to another companies that we have zero control over.

Is there a best practise for this type of activity?

VPN device on each end ?? (even though both companies are at same location) Firewall that we control and have company B connect to that? (layer 2? ) Any other option?

Cheers