The extended deadline was 4th of June 2020 for the call for participation in a pre-qualification questionnaire (PQQ) which Infrastructure Malta issued in January 2020.

It is a "all in one bag" tender. The winning company will design, build, operate and maintain the tunnel between Malta and Gozo islands. For most parts, the 14 kilometres tunnel will be partially subsea. Plans for now are for a tunnel with one lane in each direction with a service lane in between.

Four bidders have participated in the pre-qualification questionnaire for Malta - Gozo Tunnel. Two of them are consortia of companies and the other two are single companies. Two of them are very well known for their technical savviness and huge experience in similar infrastructure work but the other two are probably not so:

1- Equitix – Itochu – Yapi Merkezi – Makyol – Egis Consortium

If there is a 'Dream Team' for any insfrastructure project, this must be it. The consortium has elements solid both financially and technically. 

Equitix (https://equitix.co.uk/) is a British infrastructure investor and developer. Likely securing the financial side of the consortium.

Itochu Corporation is a Japanese insfrastructure powerhouse with a solid technology and experience for undersea tunnels.

Yapi Merkezi (https://yapimerkezi.com.tr/)  is a technically very strong Turkish contractor. They are known to be very selective in bidding for projects and afterwards being a solid performer and a finisher.

Makyol: (http://www.makyol.com.tr/en) Not much information about this Turkish company, other than they worked on they finished quite numerous tunnels. Probably the workhorse of the consortium.

Egis (https://www.egis-group.com/): This is a French government owned infrastructure company mainly active in France and France's ex-colonies.

2- WeBuild (formerly known as Salini Impregilo S.p.A.)

The Italian infrastructure giant with the technology and experience, perhaps mostly in TBM-bored tunnelling and to less degree in immersed tunnels.

https://www.webuildgroup.com/en

3- CGYI Malta Gozo Consortium

Caution: I am not sure about the exact list of companies in this consortium. This is what I was able to get via my contacts. I shall update the list later on when I get more information. For now, it is a provisional list.

China Communications Construction Co. Ltd (http://en.ccccltd.cn/): State owned Chinese construction giant. They also own the Australian construction firm John Holland. They have a lot of undersea/underwater tunnel experience like the Dalian Bay Subsea Tunnel, Nanjing Yangtze River Tunnel etc. A true giant construction company with projects from Jamaica to China to Pakistan.

Gulermak (http://www.gulermak.com.tr/taahhut/EN) : If CCCC is the giant of this consortium, Gulermak is the jewel. They are highly respected company with their civil engineering technics and experience. They have finished many projects in various countries. You see this company mostly as the underdog to a bigger company in a consortium but often Gulermak is the brains behind the success of that project.

Intertoll (https://www.intertoll.eu/)  This Hungarian company Intertoll does mainly what the name suggests. Equipment, operations etc.

YDA (https://www.yda.com.tr/en/): A relatively unknown Turkish company. According to their website, they were founded in 1954 and active in various countries. Their website lists some tunnel projects.
 

4- Malta Gozo Fixed Link Limited

A local Malta consortium which has been a champion of promoting the tunnel to the Maltese public (the Malta-Gozo video I found in youtube at the top is their work).They are for an immersed tunnel, rather than a bored one. Lead by a hospitality company (running a restaurant chain called "Hugo's"). This bid is probably the one with the least experience in tunnel construction, yet alone in infrastructure projects.