Is it possible to programmatically write to 2 different lists at the same time?

By the description of your question I guess your talking about creating multiple lists using a single feature, if that's right then yes you can have multiple list definitions associated to a single feature but I wouldn't going to recommend this as it can lead to development issues in future.

but still if you want to go it then here's a simple example,

Your Feature file will look like this,

<Feature 
Title="Feature Multiple Lists" 
Description="Feature with three lists." 
Id="put a GUID in here" 
Scope="Site" 
Version="1.0.0.0" 
Hidden="TRUE" 
xmlns="http://schemas.microsoft.com/sharepoint/">
  <ElementManifests>
    <ElementManifest Location="elementfileA.xml" />
    <ElementManifest Location="elementfileB.xml" />
    <ElementManifest Location="elementfileC.xml" />
  </ElementManifests>
</Feature>

In above feature code I declared three elementmanifest with location to a element file, element.xml contains a definition for a feature element.

Now you can declare a elementfileA with a tag for ListTemplate,

<?xml version="1.0" encoding="utf-8"?>
<Elements Id="anotherGUID" xmlns="http://schemas.microsoft.com/sharepoint/">
  <ListTemplate 
  Name="elementfileA" 
  DisplayName="DisplayName;" 
  Description="Description;" 
  BaseType="0" 
  Type="11001" 
  OnQuickLaunch="FALSE" 
  SecurityBits="11" />
</Elements>

you can create two more element files with respected names as you declared them in feature.xml, for the above listTemplate, make sure you create a new folder with same name as listtemplate e.g. in this case you will have three folders named as elementfileB, elementfileA or elementfileC with each list's schema.xml in them.

For more information on this you can look at this MSDN article

However if you want to add multiple lists using code then you can try something like this,

using (SPSite oSPsite = new SPSite("http://Web URL"))
{
    oSPsite.AllowUnsafeUpdates = true;

    using (SPWeb oSPWeb = oSPsite.OpenWeb())
    {
        oSPWeb.AllowUnsafeUpdates = true;

        /* 1. create list from custom ListTemplate present within ListTemplateGalery */
        SPListTemplateCollection lstTemp = oSPsite.GetCustomListTemplates(oSPWeb);
        SPListTemplate template = lstTemp["custom template name"];
        oSPWeb.Lists.Add("List Name 1", "Description", template);


        /* 2. create list from sharepoint list content type (e.g. Links) */
        oSPWeb.Lists.Add("List Name 2", "Description", SPListTemplateType.Links);

        oSPWeb.AllowUnsafeUpdates = false;
    }

    oSPsite.AllowUnsafeUpdates = false;
}

For more information on creating a list using check this Link out

I am no master so if you see any mistake let me know,

hope it helps :)